Wireless communication terminal device and power allocation method

ABSTRACT

Provided are a wireless communication terminal device and a power allocation method, wherein transmission channel quality information, regarding a Pcell having a high probability that UCI is multiplied therein, can be accurately estimated by an SRS having high priority in power allocation, and an eNB can instruct appropriate transmission power to an UL channel which transmits the subsequent UCI. A power scaling detection unit detects whether or not a total transmission power value of the UL channels transmitted by the plurality of CC exceeds the maximum transmission power specific to the UE. When a plurality of SRS are simultaneously transmitted using a Pcell and a Scell, and power scaling occurs, a power scaling control unit performs power allocation so that transmission power of the SRS of the Pcell has the higher priority than that of the SRS of the Scell.

TECHNICAL FIELD

The present invention relates to a radio communication terminalapparatus and a power allocation method.

BACKGROUND ART

In 3rd Generation Partnership Project (3GPP), studies have been carriedout on LTE-Advanced (hereinafter, abbreviated as “LTE-A”). In LTE-A, theintroduction of a bandwidth expansion technology called “carrieraggregation (CA)” has been studied. In LTE-A carrier aggregation, anapproach is taken in downlink (DL) and uplink (UL) channels thatachieves high speed transmission by aggregating a plurality of carriers,i.e., by bundling component carriers (CCs) each having 20 MHz, forexample. In LTE-A, studies have been carried out on bandwidth expansionthrough the introduction of five CCs, i.e., up to 100 MHz, as a possiblerange.

In this respect, studies have been carried out at the same time on atransmission power control method targeting UL CA. In the studies on ULtransmission power control in LTE-A, the following matters (A) to (C)have been agreed. CC-specific transmission power control is performed(A). CC-specific (for each UL channel) maximum transmission power Pcmax,c, and UE (User Equipment) specific (UE-specific) maximum transmissionpower Pcmax (upper limit of total maximum transmission power on aplurality of CCs) are provided (B). In addition, when the transmissionpower of each UL channel transmitted on one CC exceeds the CC-specific(for each UL channel) maximum transmission power, or when the totalvalue of transmission power of UL channels transmitted on a plurality(all) of CCs in simultaneous transmission of a plurality of UL channelsexceeds a UE-specific maximum transmission power, control called powerscaling, which reduces the transmission power of a UL channel, isperformed (B). In UL CA, the power allocation priority rule for aplurality of UL channels when power scaling occurs in simultaneoustransmission of a plurality of UL channels is agreed as follows (C).

-   -   PUCCH>PUSCH with UCI>PUSCH without UCI

PUCCH stands for Physical Uplink Control CHannel, and PUSCH stands forPhysical Uplink Shared CHannel. UCI is an abbreviation for UplinkControl Information, and for example, includes the following controlinformation, specifically. UCI includes acknowledgment/nonacknowledgment (ACK/NACK), rank indicator (RI), channel qualityinformation (CQI), pre-coding matrix indicator (PMI) and channel stateinformation (CSI). A periodic or aperiodic transmission method is usedfor transmitting the information such as CSI and CQI, for example.

In addition, the term “PUSCH with UCI” refers to a PUSCH on which UCI ismultiplexed, and the term “PUSCH without UCI” refers to a PUSCH on whichno UCI is multiplexed. Accordingly, when power scaling occurs insimultaneous transmission of a plurality of UL channels, thetransmission power is allocated in the following order: the transmissionpower for PUCCH; the transmission power for PUSCH on which UCI ismultiplexed; and the transmission power for PUSCH on which no UCI ismultiplexed. This rule applies regardless of whether these channels areon the same CC or on different CCs.

Meanwhile, studies have been carried out on a power allocation rule usedwhen power scaling relating to a periodic sounding reference symbol(SRS) or an aperiodic SRS used for measuring a channel quality such asCQI occurs. The power allocation rule can be classified into thefollowing three cases (A) to (C), for example.

(A) Priority between a (periodic/aperiodic) SRS and a different ULchannel (such as PUCCH or PUSCH) is as follows. Specifically, Non-PatentLiterature (hereinafter, abbreviated as “NPL”) 1 describes the followingpriority used when power scaling occurs.

-   -   PUCCH>SRS>PUSCH

Accordingly, when power scaling occurs, the transmission power for aterminal is preferentially allocated in the order of a PUCCH, an SRS,and a PUSCH.

(B) Priority between a periodic SRS and an aperiodic SRS is as follows.Specifically, NPL 2 describes the following priority used when powerscaling occurs.

-   -   Aperiodic SRS>Periodic SRS

Accordingly, when power scaling occurs in simultaneous transmission of aperiodic SRS and an aperiodic SRS, the transmission power ispreferentially allocated in the order of an aperiodic SRS, and aperiodic SRS.

(C) Priority between a plurality (periodic or aperiodic) of SRSes is asfollows.

NPL 1 describes a power allocation priority rule used when a pluralityof periodic SRSes are simultaneously transmitted on a plurality of CCs.Specifically, NPL 1 discloses a method of determining priority fortransmission power for periodic SRSes in accordance with UL CC IDnumbers as illustrated in FIG. 1. FIG. 1 is a conceptual diagram forallocating larger transmission power in descending order of ID numbersof UL CCs when power scaling occurs in simultaneous transmission ofperiodic SRSes on three CCs. Accordingly, each terminal canappropriately determine the transmission power of a periodic SRS foreach of the CCs in accordance with this rule even when power scalingoccurs in simultaneous transmission of periodic SRSes on a plurality ofCCs.

CITATION LIST Non-Patent Literatures

NPL 1

-   R1-105376, Discussion on multiplexing SRS and PUSCH in an SC-FDMA    symbol in carrier-aggregated system, 3GPP TSG RAN WG1 #62bs, Xi'an,    China, Oct. 11-15, 2010

NPL 2

-   R1-105508, Power control for SRS transmission in CA, 3GPP TSG RAN    WG1 #62bs, Xi'an, China, Oct. 11-15, 2010

NPL 3

-   3GPP TS 36.213 V8.8.0 (2009-09)

SUMMARY OF INVENTION Technical Problem

The technique disclosed in NPL 1 has the following problems, however.Specifically, the technique does not take into account the effects ofthe method of selecting a CC for multiplexing important UCI to which noretransmission is applied, on the power allocation priority used whenpower scaling occurs in simultaneous transmission of a plurality ofperiodic SRSes on a plurality of CCs. Since UCI needs to be reported toan eNB from a terminal with low delay, only single transmission issupported for UCI.

Accordingly, when a CC configured with lower power allocation prioritybased on the technique disclosed in NPL 1 (CC that is likely to have alarger CQI measurement error in the eNB) is used as a CC on which UCI isto be multiplexed, the measurement error of communication quality (e.g.,Signal-to-Interference plus Noise power Ratio (SINR)) on the CC, whichis derived using an SRS subjected to power scaling (transmission poweris reduced), is large. Accordingly, the eNB cannot report an appropriatetransmission power (or Modulation and channel Coding Scheme (MCS)) valuefor the UCI to be transmitted in a subsequent subframe. It should benoted that, power scaling occurs according to transmission power controlinformation related to a UE-specific power amplifier (PA) that an eNBcannot know, e.g., a parameter (such as Maximum Power Reduction (MPR))for determining the maximum transmission power for each UE or each CC ofa UE, the eNB does not know whether power scaling has occurred,basically.

When a UE performs power scaling (reduction of transmission power) foran SRS on a certain CC of a smaller UL CC ID number based on thetechnique disclosed in NPL 1 because the transmission power exceeds theUE-specific maximum transmission power in simultaneous transmission of aplurality of SRSes on a plurality of CCs, for example, the eNB measuresthe communication quality of the CC using a received SRS with a reducedreception level. As described above, since the eNB, however, has noinformation indicating when power scaling has occurred for the terminal,basically, the eNB erroneously recognizes the reason for reduction inthe SRS reception level as being deterioration in the quality of themobile communication channel, which easily changes with time, instead ofthe occurrence of power scaling in the terminal. In addition, the eNBreports an instruction to use a large transmission power value (smallMCS value) not less than a value required to satisfy predeterminedreception quality for transmission of a subsequent UL channel (on whichUCI is multiplexed) such as a PUSCH. Stated differently, transmission ofa UL channel with excessive quality is performed for a subsequent ULchannel such as a PUSCH in this case (co-channel interference to anothercell is increased when an instruction to increase the transmission poweris transmitted. In addition, another problem such as an unnecessaryincrease in the power consumption of the terminal is caused).

It is an object of the present invention to provide a radiocommunication terminal apparatus and a power allocation method each ofwhich enables highly accurate estimation of propagation channel qualityinformation on a Pcell that is likely to be multiplexed with UCI, usingan SRS with high power allocation priority, and which also enables aneNB to indicate appropriate transmission power for a subsequent ULchannel for transmitting UCI.

Solution to Problem

A radio communication terminal apparatus according to an aspect of thepresent invention, includes: a transmission power calculating sectionthat calculates transmission power of a plurality of uplink channels ona plurality of component carriers of carrier aggregation; a powerscaling detecting section that detects, using the calculatedtransmission power, whether or not a total value of the transmissionpower of the uplink channels transmitted on the plurality of componentcarriers exceeds maximum transmission power specific to the apparatusand whether or not power scaling occurs as a result; and a power scalingcontrolling section that preferentially allocates, when power scalingdetecting section detects that power scaling occurs and when a pluralityof reference signals is transmitted using a primary cell and a secondarycell, transmission power with respect to a reference signal of theprimary cell over a reference signal of the secondary cell.

A power allocation method according to an aspect of the presentinvention, includes: a transmission power calculating step ofcalculating transmission power of a plurality of uplink channels on aplurality of component carriers of carrier aggregation; a power scalingdetecting step of detecting, using the calculated transmission power,whether or not a total value of the transmission power of the uplinkchannels transmitted on the plurality of component carriers exceedsmaximum transmission power specific to a corresponding apparatus andwhether or not power scaling occurs as a result; and a power scalingcontrolling step of preferentially allocating, when power scalingdetecting section detects that power scaling occurs and when a pluralityof reference signals is transmitted using a primary cell and a secondarycell, transmission power with respect to a reference signal of theprimary cell over a reference signal of the secondary cell.

Advantageous Effects of Invention

According to the present invention, propagation channel qualityinformation on a Pcell that is likely to be multiplexed with UCI can beestimated with high accuracy using an SRS with high power allocationpriority, and also, an eNB can indicate appropriate transmission powerfor a subsequent UL channel for transmitting UCI.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a method of determining priority oftransmission power disclosed in NPL 1;

FIG. 2 is a block diagram illustrating a configuration of a radiocommunication terminal apparatus according to Embodiments 1 and 2 of thepresent invention;

FIG. 3 is a diagram illustrating a configuration in which an SRS ismultiplexed at the end portion of a subframe;

FIG. 4 is a diagram illustrating an overview of power scaling method 1;

FIG. 5 is a diagram illustrating an overview of power scaling method 2;

FIG. 6 is a diagram illustrating an overview of power scaling method 3;

FIG. 7 is a diagram illustrating how two SRSes are dropped;

FIG. 8 is a diagram illustrating how a periodic SRS is dropped;

FIG. 9 is a diagram illustrating an overview of power scaling method 4;

FIG. 10 is a diagram illustrating an overview of power scaling method 5;

FIG. 11 is a diagram illustrating an overview of power scaling method 6;

FIG. 12 is a diagram illustrating an overview of power scaling method 7;

FIG. 13 is a diagram illustrating an overview of power scaling method 8;

FIG. 14 is a diagram illustrating an overview of power scaling method11;

FIG. 15 is a diagram illustrating an overview of power scaling method12;

FIG. 16 is a diagram illustrating a configuration in which a PUCCH and aperiodic SRS are multiplexed in a subframe;

FIG. 17 is a diagram illustrating an overview of power scaling method13;

FIG. 18 is a block diagram illustrating a configuration of a radiocommunication terminal apparatus according to Embodiment 1 of thepresent invention;

FIG. 19 is a diagram illustrating a configuration in which a PUSCH and aperiodic SRS are multiplexed in a subframe;

FIG. 20 is a diagram illustrating an overview of power scaling method14; and

FIG. 21 is a diagram illustrating an overview of power scaling method15.

DESCRIPTION OF EMBODIMENTS

The inventors of the present invention have made the invention withcareful observation of the following points. Specifically, when a PUSCHis scheduled with a primary cell (Pcell) or primary component carrier(PCC) (i.e., to be transmitted with transmission assignment (UL grant))in LTE-A, UCI is multiplexed with the PUSCH on a Pcell (PCC) as a methodfor selecting a CC (PUSCH) for multiplexing UCI. In addition, the CCused for transmitting a PUCCH (i.e., for multiplexing only UCI) islimited to only a Pcell (PCC). Accordingly, as compared with a secondarycell (Scell) or secondary component carrier (SCC), it is likely that UCIwith high priority to which no retransmission is applied is transmittedusing a Pcell (PCC).

In addition, when there is not much traffic during system operation,only a Pcell is preferentially used in general (Pcell is selected as acell that allows easier communication over a long period of time), whichimproves the spectral efficiency of the system bandwidth (betweenoverall CCs). Moreover, PUCCH transmission is backward compatible withLTE Release 8 when a Pcell is used, so that efficient transmission ismade possible on the PUCCH on which only UCI is transmitted(incidentally, LTE-A is planned to be released with Release 10).

In addition, an eNB configures a UE with a UE-specific Pcell (PCC) andScell (SCC) and notifies the UE of the UE-specific Pcell and Scell(e.g., via higher layer signaling with extremely low transmission errorrate), so that both of the eNB and each UE can recognize the Pcell (PCC)and Scell (SCC) configuration in advance.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

Embodiment 1

FIG. 2 is a block diagram illustrating a configuration of radiocommunication terminal apparatus (hereinafter, referred to as“terminal”) 100 according to Embodiment 1 of the present invention.Hereinafter, the configuration of terminal 100 will be described usingFIG. 2.

Radio reception processing section 102 receives, via antenna 101, anOFDM signal transmitted from a base station (eNB), performspredetermined RF processing such as down-conversion, A/D conversionand/or the like on the received OFDM signal and outputs the processedsignal to OFDM demodulation section 103.

OFDM demodulation section 103 removes a guard interval (GI) from theOFDM signal outputted from radio reception processing section 102 andperforms a discrete Fourier transform (DFT) on the OFDM signal fromwhich the GI has been removed, to transform the signal into afrequency-domain signal. Next, OFDM demodulation section 103 performsfrequency-domain equalization (FDE) and/or the like on the components ofthe frequency domain to remove signal distortion, and outputs theprocessed signal to demodulation section 104.

Demodulation section 104 performs predetermined demodulation processingfor a modulation scheme such as QPSK or 16QAM (Quadrature AmplitudeModulation) on the signal outputted from OFDM demodulation section 103and outputs the processed signal to channel decoding section 105.

Channel decoding section 105 performs decoding processing (iterative MAPdecoding or Viterbi decoding) for error correction coding such as turbocoding and convolutional coding on the signal outputted fromdemodulation section 104.

Control information extraction section 106 extracts control informationfrom the signal outputted from channel decoding section 105 and outputsthe extracted control information to transmission power calculatingsection 107. The control information to be extracted herein includes: ULgrant information (allocation bandwidth, MCS set, PUSCH, SRS or PUCCHtransmission power information (TPC command, transmission formatdependent value Δ_(TF) such as MCS, and SRS offset value P_(SRS) _(_)_(offset)), and aperiodic SRS trigger information, for example), DLgrant information (transmission power information on PUCCH or the like,and aperiodic SRS trigger information, for example), UCI request(trigger) information, CC/cell information such as Pcell/Scell andPCC/SCC.

Transmission power calculating section 107 calculates transmission powerof a plurality of UL channels (on each CC) using the control informationoutputted from control information extraction section 106, CC-specific(each UL channel) maximum transmission power (such as power class ofpower amplifier (PA) and MPR), path-loss (estimate) information,transmission power related reporting information on a higher layer(path-loss compensation coefficient, P_o (target reception level value)and/or the like), for example. As a specific calculation method, PUSCH,PUCCH and SRS transmission power calculation formulae described in NPL 3are used, for example. Transmission power calculating section 107outputs transmission power values of a plurality of UL channels (on eachCC) to power scaling detecting section 108 and power scaling controllingsection 109.

Power scaling detecting section 108 calculates total transmission powerof a plurality of CCs (all UL channels) from the transmission powervalues of a plurality of UL channels outputted from transmission powercalculating section 107 and compares the calculated total transmissionpower with UE-specific maximum transmission power (Pcmax) to bereceived.

When the total transmission power is smaller than the UE-specificmaximum transmission power, control information indicating “powerscaling is unnecessary” is outputted to power scaling controllingsection 109. On the other hand, when the total transmission power islarger than the UE-specific maximum transmission power, controlinformation indicating “power scaling is necessary” is outputted topower scaling controlling section 109.

In accordance with information indicating the presence or absence ofoccurrence of power scaling outputted from power scaling detectingsection 108, power scaling controlling section 109 performs transmissionpower scaling on each UL channel (such as SRS, PUSCH and PUCCH) when thecontrol information indicates “power scaling is necessary,” to determinethe transmission power for each of the plurality of UL channels (CCs).The transmission power information after power scaling is outputted totransmission power setting sections 112-1 to 112-N. The details of anSRS power scaling method will be described hereinafter.

Coding and modulation sections 110-1 to 110-N perform error correctioncoding such as turbo coding and predetermined modulation processing suchas QPSK or 16QAM on a transport block (TB) for each CC to be received,and output the resultant signal to multiplexing sections 111-1 to 111-N.

Multiplexing sections 111-1 to 111-N multiplex a periodic SRS (whentriggered by higher layer control information) or aperiodic SRS (whentriggered by a PDCCH of the physical layer control channel) to bereceived, with a modulation symbol sequence and outputs the resultantsignal to transmission power setting sections 112-1 to 112-N. In LTE(LTE-A), an SRS is multiplexed only at the last symbol of one subframeconsisting of 14 SC-FDMA symbols as illustrated in FIG. 3 (when SRS istime-multiplexed with PUSCH). Thus, in order to allow such time-domainmultiplexing, an SRS is multiplexed at the last symbol of the modulationsymbols. FIG. 3 illustrates a state where a demodulation referencesignal occupies roughly three symbols (DMRS) on a center portion of asubframe.

Transmission power setting sections 112-1 to 112-N set the transmissionpower for each UL channel (such as SRS, PUSCH and PUCCH) using thetransmission power information on each of the plurality of UL channels(CCs) outputted from power scaling controlling section 109 and outputthe transmission power to SC-FDMA modulation section 113-1 to 113-N.

SC-FDMA modulation section 113-1 to 113-N perform precoding by applyinga DFT on the symbol sequences on which the transmission power is set andwhich are outputted from transmission power setting sections 112-1 to112-N. After the signals subjected to DFT precoding are mapped topredetermined frequency resources indicated by the eNB, the processedsignals are transformed into time-domain signals by IDFT. Lastly, theprocessed signals after addition of a guard interval are outputted tocombining section 114.

Combining section 114 combines the plurality of SC-FDMA signalsoutputted from SC-FDMA modulation sections 113-1 to 113-N and outputsthe combined signal to radio transmission processing section 115.

Radio transmission processing section 115 performs predetermined RFprocessing such as D/A conversion, amplification processing, andup-conversion on the signal outputted from combining section 114 andtransmits the processed signal to antenna 101.

Next, power scaling methods 1 to 12 for SRSes in simultaneoustransmission of a plurality of SRSes will be described.

Power Scaling Method 1

In power scaling method 1, transmission power calculating section 107calculates transmission power of a plurality of UL channels of aplurality of CCs, first.

Next, power scaling detecting section 108 detects whether or not thetotal value of transmission power of the UL channels transmitted on theplurality of CCs exceeds the UE-specific maximum transmission power(whether or not power scaling occurs).

Next, when power scaling occurs in simultaneous transmission of aplurality of (periodic or aperiodic) SRSes using a Pcell (PCC) and Scell(SCC), power scaling controlling section 109 preferentially allocatestransmission power with respect to an SRS of a Pcell over an SRS of anScell of the plurality of (periodic or aperiodic) SRSes to betransmitted simultaneously.

FIG. 4 illustrates an overview of power scaling method 1. In FIG. 4, theSRSes are simultaneously transmitted on three CCs (CC#0 to CC#2). Forexample, only SRSes are transmitted on the three CCs using the lastsymbol position of one subframe (see, FIG. 3). According to the controlsignal reported from the base station (via higher layer signaling),CC#0, CC#1, and CC#2 are configured as an Scell, Pcell, and Scell,respectively. FIG. 4 illustrates the operation to preferentiallyallocate transmission power with respect to the SRS on CC#1 configuredas a Pcell over the SRSes on CC#0 and CC#2 each configured as an Scell,when the total value of transmission power of the SRS channels on thethree CCs transmitted as a plurality of CCs exceeds the UE-specificmaximum transmission power in this situation.

Accordingly, it is possible to reduce the probability of a CC thattransmits an SRS with low power allocation priority (i.e., CC that islikely to have a larger CQI measurement error) being identical to a CCon which UCI is to be multiplexed. For example, the probability of theScells of CC#0 and CC#2 with low power allocation priority beingidentical to a CC on which UCI is to be multiplexed can be reduced asillustrated in FIG. 4. Thus, the propagation channel quality information(Channel Quality Indicator (CQI)) on the Pcell on which UCI is likely tobe multiplexed can be estimated with high accuracy by the SRS with highpower allocation priority. Accordingly, the eNB can indicate appropriatetransmission power (MCS) for a subsequent UL channel transmitting UCI(e.g., PUSCH on which data and UCI are multiplexed, PUCCH on which UCIis multiplexed, and/or the like). Stated differently, it is possible totransmit UCI without setting excessive quality for the transmissionformat used for the UL channel transmitting the UCI. In addition,transmission can be performed without any unnecessary increase of theco-channel interference to another cell or in power consumption of theterminal.

Power Scaling Method 2

In power scaling method 2, power scaling controlling section 109performs power scaling by setting the transmission power of the SRS of aPcell to be not greater than the CC-specific (for each UL channel)maximum transmission power (while satisfying the CC-specific maximumtransmission power condition), then keeping (not changing) thetransmission power of the SRS of the Pcell, and reducing thetransmission power of an Scell.

FIG. 5 illustrates an overview of power scaling method 2. In FIG. 5, theSRSes are simultaneously transmitted on three CCs (CC#0 to CC#2).According to the control signal reported from the base station (viahigher layer signaling), CC#0, CC#1, and CC#2 are configured as anScell, Pcell, and Scell, respectively. FIG. 5 illustrates the operationto perform power scaling by keeping (not changing) the transmissionpower of the SRS on CC#1 configured as a Pcell, and reducing thetransmission power of the SRSes on CC#1 and CC#2 each configured as anScell, when the total value of transmission power of SRS channels on thethree CCs transmitted as a plurality of CCs exceeds the UE-specificmaximum transmission power in this situation.

Accordingly, setting the transmission power of the SRS of a Pcell insuch a way that the condition that the transmission power of the SRS ofa Pcell is equal to or less than the maximum transmission power of eachCC (each UL channel) makes it possible to maintain co-channelinterference to another cell from each CC to be equal to or less than acertain predetermined value and also makes scheduling for each CC andcross-carrier scheduling performed by each eNB easier. In addition,surely keeping (not allowing any change) the transmission power level ofthe SRS of a Pcell allows the propagation channel quality of the Pcellby a (periodic or aperiodic) SRS to be measured with even higheraccuracy than that in the case of power scaling method 1.

In other words, it is possible to prevent the communication qualityinformation on a Pcell that is obtained from the received SRS of thePcell from being affected by power scaling in the terminal (to avoidmisrecognition of the UE transmission power between the UE and eNB).Thus, the eNB can perform more appropriate operation in subsequentscheduling (resource allocation) and transmission power (AdaptiveModulation channel Coding (AMC)) control for the Pcell on which UCI islikely to be transmitted. Accordingly, it is possible to obtain theeffect of eliminating the need for passive control such as setting alarge margin for transmission power (AMC) control.

Power Scaling Method 3

In power scaling method 3, power scaling controlling section 109performs power scaling by keeping (not changing) the transmission powerof the SRS of a Pcell, and dropping the SRS of an Scell (this means thatno SRS is transmitted or transmission power is set equal to zero(transmission power=0)).

FIG. 6 illustrates an overview of power scaling method 3. As in FIGS. 4and 5, the SRSes are simultaneously transmitted on three CCs (CC#0 toCC#2) in FIG. 6. According to the control signal reported from the basestation (via higher layer signaling), CC#0, CC#1, and CC#2 areconfigured as an Scell, Pcell, and Scell, respectively. FIG. 6illustrates the operation to perform power scaling by keeping (i.e., notchanging) the transmission power of the SRS on CC#1 configured as aPcell, and dropping the SRS on CC#2 configured as an Scell, when thetotal value of transmission power of SRS channels of the three CCstransmitted as a plurality of CCs exceeds the UE-specific maximumtransmission power in this situation.

Accordingly, dropping the SRS of an Scell enables simplification ofcomplex power allocation control between CCs in addition to obtainingthe effects brought about by power scaling method 1. In LTE-A, an SRS ismultiplexed only at the last symbol of one subframe consisting of 14symbols. Accordingly, even when the last symbol alone is dropped, theinfluence on the spectrum efficiency is small. For example, when an SRSis transmitted only on one CC, the impact of dropping the symbol isequal to 7% ( 1/14=7%). Moreover, the frequency (cycle) of SRStransmission is, for example, once in 10 ms for periodic SRS, which isvery low as compared with the frequency of data transmission. Thus, theinfluence on the spectrum efficiency is even smaller (data can betransmitted once in 1 ms at minimum).

In addition, dropping the SRS enables easier detection of the occurrenceof power scaling in a terminal during blind detection processing on SRSreception power in an eNB. This is because, setting the transmissionpower of the SRS of an Scell (SCC) to be equal to zero (no SRStransmission) when power scaling occurs in simultaneous transmission ofa plurality of SRSes allows an eNB to easily determine that powerscaling has occurred when the eNB can only measure a received SRS levelas low as a noise level during an SRS reception period, for example.Accordingly, it is possible to avoid transmitting a wrong instruction ontransmission power (MCS) to a terminal for a subsequent subframe (e.g.,transmitting an instruction resulting in excessive quality). Forexample, when detecting a significant decrease in the SRS receptionlevel (value as low as a noise level), the eNB can instruct the terminalto retransmit (trigger) an SRS with an appropriate transmission powervalue for the SRS again.

Although Embodiment 1 is described with a case where power scalingmethod 3 is applied when power scaling occurs in simultaneoustransmission of a plurality of SRSes on a plurality of CCs, it ispossible to drop the SRS of an Scell in simultaneous transmission ofSRSes of a Pcell and Scell even when no power scaling occurs. Moreover,it is also possible to uniformly drop all the SRSes on a plurality ofScells. FIG. 7 illustrates a case where two SRSes respectively on CC#0and CC#2 are dropped in simultaneous transmission of SRSes on CC#0 toCC#2. Thus, it is possible to omit the arithmetic operation required forpower allocation processing between CCs while obtaining the same effectsas those described above, and also to significantly reduce the man hoursfor testing terminals (or eNBs) with respect to power scaling, which isindispensable for the commercialization of LTE-A.

In addition, when a periodic SRS and aperiodic SRS are transmitted usingScells, a periodic SRS may be preferentially dropped over an aperiodicSRS. Furthermore, this method can be applied to the case where powerscaling occurs in simultaneous transmission of a plurality of SRSes on aplurality of CCs (A) or the case where no power scaling occurs insimultaneous transmission of a plurality of SRSes of a Pcell and Scell(B).

An aperiodic SRS is the SRS that is newly introduced into LTE-A andconfigured to be triggered by a PDCCH, which is a physical layerdownlink control channel, for an eNB to measure new quality informationwith low delay. Meanwhile, a periodic SRS (of transmission cycle,trigger, timer and/or the like) is configured by higher layer signaling,so that only low speed control is possible. Accordingly, the feature ofan aperiodic SRS (for eNB to make immediate determination on CQImeasurement using SRS) can be reflected in power scaling processing, andthe same effects as those described above can be obtained. In addition,the effect of reducing the man hours for testing terminals (or eNBs)with respect to power scaling can be obtained in the case describedabove (B).

FIG. 8 illustrates how the periodic SRS of the Scell of CC#2 is droppedwhen the aperiodic SRS is triggered on the Scell of CC#0 and theperiodic SRS is triggered on the Scell of CC#2 while nothing istransmitted on the Pcell of CC#1 at the same symbol position of the samesubframe (e.g., the last symbol position of a subframe).

Power Scaling Method 4

In power scaling method 4, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 reduces (drop or settingthe transmission power to be equal to zero (no SRS transmission)) thetransmission power in ascending order of the transmission power of SRSesof the Scells (or the smallest) (while keeping the transmission power ofthe SRS of the Pcell).

FIG. 9 illustrates an overview of power scaling method 4. As in FIGS. 4and 5, the SRSes are simultaneously transmitted on the three CCs (CC#0to CC#2) in FIG. 9. According to the control signal reported from thebase station (via higher layer signaling), CC#0, CC#1, and CC#2 areconfigured as an Scell, Pcell, and Scell, respectively. In addition, thetransmission power of the SRS of the Scell before power scaling islarger for the SRS on CC#2 than for the SRS on CC#0. FIG. 9 illustratesthe operation to perform power scaling by preferentially dropping theSRS transmission on CC#0 configured as the Scell with smallertransmission power (or the smallest) when the total value oftransmission power of the SRS channels on the three CCs transmitted as aplurality of CCs exceeds the UE-specific maximum transmission power inthis situation.

Accordingly, since an SRS with smaller transmission power is more likelyto fall below an SRS detection level capable of being received by an eNB(e.g., noise level at eNB), preferentially reducing the transmissionpower of the SRS of an Scell with smaller transmission power makes itpossible to maintain the accuracy in measurement using the SRS of theScell from which no transmission power is reduced, while maintaininghighly accurate quality measurement on a Pcell.

Power Scaling Method 5

In power scaling method 5, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 uniformly reduces thetransmission power of the plurality of SRSes of the Scells (reduces thesame transmission power value or applies the same scaling (weighting))(while keeping (not changing) the transmission power of the SRS of aPcell).

FIG. 10 illustrates an overview of power scaling method 5. As in thecase described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 10. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 10 illustrates how the transmission power of CC#0 and CC#2configured as the Scells is uniformly reduced when the total value oftransmission power of the SRS channels on the three CCs transmitted as aplurality of CCs exceeds the UE-specific maximum transmission power inthis situation. Examples of the method used to uniformly reduce thetransmission power include a method to reduce the transmission powerwith the same value (true value or decibel value) or to apply the samescaling (weight) (applied in LTE-A). Meanwhile, as the scaling weightused for reducing the transmission power of SRSes, a scaling weight forSRSes may be used, or the same scaling weight as that for another uplinkchannel (e.g., PUSCH) may be used for SRSes. The term “scaling weight”used herein refers to a parameter that is previously reported to aterminal from an eNB.

Accordingly, it is possible to enable simplification of complex powerallocation control between CCs while maintaining highly accurate qualitymeasurement on a Pcell.

Power Scaling Method 6

In power scaling method 6, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 drops all the SRSes ofthe Scells (uniformly drops SRSes of Scells) (stops the transmission orsets the transmission power to be equal to zero).

FIG. 11 illustrates an overview of power scaling method 6. As in thecase described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 11. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 11 illustrates how the SRSes on CC#0 and CC#2 configured as theScells are uniformly dropped when the total value of transmission powerof the SRS channels of the three CCs transmitted as a plurality of CCsexceeds the UE-specific maximum transmission power in this situation.

Accordingly, it is possible to enable simplification of complex powerallocation control between CCs while obtaining the effects similar tothose obtained with power scaling method 3. In addition, the man hoursfor testing terminals (or eNBs) with respect to power scaling, which isindispensable for the commercialization of LTE can be significantlyreduced. For example, although it is required to determine thespecifications for testing all combinations of SRSes of a plurality ofScells to be transmitted, the man hours for the testing itself or fordetermining the specifications for the testing can be reduced.

It should be noted that, when a plurality of SRSes is present in Scells,instead of uniformly dropping all the SRSes, it is possible to drop theSRSes in (ascending/descending) order of the CC (cell) numbers.

Power Scaling Method 7

In power scaling method 7, when transmission power of a certain SRS of aplurality of SRSes is smaller than the SRS having the largesttransmission power among the SRSes by at least the amount of apredetermined threshold, power scaling controlling section 109 reducesthe transmission power of the certain SRS of the Scell or drops thecertain SRS (stops the transmission or sets the transmission power to beequal to zero).

FIG. 12 illustrates an overview of power scaling method 7. As in thecases described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 12. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 12 illustrates how the SRS of the Scell is dropped when the totalvalue of transmission power of the SRS channels of the three CCstransmitted as a plurality of CCs exceeds the UE-specific maximumtransmission power and also when a difference between the transmissionpower of the SRS having the largest transmission power among theplurality of SRSes and the SRS of the Scell is at least a predeterminedthreshold in this situation described above. FIG. 12 illustrates a casewhere the difference between the transmission power of the SRS of theScell of CC#2 and the transmission power of the SRS of the Pcell ofCC#1, which is the largest among the plurality of SRSes, is at least apredetermined value.

When a difference in the transmission power of SRS between CCs is large,there occurs a situation where the intermodulation distortion of the SRSon the CC with larger transmission power becomes larger than thetransmission power of the SRS on a different CC. The intermodulationdistortion cannot be removed by a transmission filter. In other words,when the SRS is transmitted without removal of the intermodulationdistortion, the eNB measures the communication quality of the CC by theSRS affected by the intermodulation distortion. As a result, correctscheduling or transmission power control cannot be performed.Accordingly, this problem can be avoided by dropping the SRS of theScell when the difference between the largest SRS transmission power andthe SRS transmission power of the Scell is at least a predeterminedthreshold.

As a method of setting the threshold, it is possible to set a certainvalue and to adaptively change the value according to a path-loss(measurement) value.

In addition, instead of the transmission power of an SRS having thelargest transmission power among a plurality of SRSes, the transmissionpower of a channel having the largest transmission power among ULchannels to be simultaneously transmitted may be set as the referencevalue. Accordingly, the same effects can be obtained with thisconfiguration.

Power Scaling Method 8

In power scaling method 8, when transmission power of a certain SRS ofan Scell is not greater than a predetermined threshold, power scalingcontrolling section 109 reduces the transmission power of the SRS of theScell or drops the SRS (stops the transmission or sets the transmissionpower to be equal to zero).

FIG. 13 illustrates an overview of power scaling method 8. As in thecases described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 13. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 13 illustrates how the SRS of the Scell is dropped when the totalvalue of transmission power of the SRS channels of the three CCstransmitted as a plurality of CCs exceeds the UE-specific maximumtransmission power and also when the transmission power of the pluralityof SRSes of the Scell is not greater than a certain threshold in thissituation described above.

When the transmission power of an SRS on a CC is too small, thetransmission signal cannot be correctly expressed with the resolution ofthe digital/analog (D/A) converter of the terminal (transmission side).However, the introduction of a threshold and dropping an SRS havingtransmission power not greater than the threshold make it possible toavoid unnecessary transmission processing (i.e., complex designing ofD/A taking into account (covering) low transmission power values)(consuming unnecessary transmission power can be avoided).

Power Scaling Method 9

In power scaling method 9, power scaling controlling section 109 selectsan SRS on a CC to be dropped (e.g., power allocation priority islowered, transmission power is reduced, transmission is stopped, ortransmission power is set equal to zero), in accordance with the lengthof the transmission cycle of a periodic SRS. Specifically, power scalingcontrolling section 109 selects a periodic SRS of a long transmissioncycle as the SRS on a CC to be preferentially dropped or a periodic SRSof a short transmission cycle as the SRS on a CC to be preferentiallydropped.

When an SRS of a long transmission cycle is selected as the SRS on a CCto be preferentially dropped, it is possible to obtain the same effectsas those obtained with power scaling method 3 and also to preferentiallyfollow short-term channel variation and achieves adaptive modulation andchannel coding (AMC) in accordance with short-term fading variation andalso to control time-frequency domain scheduling with high accuracy.Thus, UE-specific throughput and system throughput by multi-userdiversity can be improved.

When an SRS of a short transmission cycle is selected as the SRS on a CCto be preferentially dropped, it is possible to obtain the same effectsas those obtained with power scaling method 3 and also to improve thelong-term channel measurement accuracy. Thus, cross-carrier schedulingcontrol, which adaptively selects a CC used for transmitting data andcontrol information, can be performed with high accuracy.

Power Scaling Method 10

In power scaling method 10, power scaling controlling section 109selects an SRS on a CC to be dropped (e.g., power allocation priority islowered, transmission power is reduced, transmission is stopped, ortransmission power is set equal to zero), in accordance with thebandwidth of each SRS. Specifically, an SRS having a wide bandwidth ispreferentially dropped over an SRS having a narrow bandwidth, or an SRShaving a narrow bandwidth is preferentially dropped over an SRS having awide bandwidth.

When an SRS having a wide bandwidth is preferentially dropped over anSRS having a narrow bandwidth, the following effects can be obtained.The transmission power of a UL channel (such as PUSCH and SRS) of LTE-A(LTE) is determined based on the transmission bandwidth and powerspectrum density (PSD). Thus, reducing the transmission power allocationpriority of an SRS having a wide bandwidth that has a large influence onthe size of the total transmission power makes it possible to minimizethe number of SRSes to be dropped. For example, provided that the totalbandwidth of SRSes on a plurality of CCs is defined as B, comparing thecase where the bandwidth of the SRS on one CC is B with the case wherethe bandwidth of each of the SRSes on two CCs is B/2, the number of CCsto be dropped can be smaller when the SRS on one CC is preferentiallydropped. Such a decrease in the number of CCs to be dropped is veryadvantageous when sounding on as many CCs as possible using SRSes isperformed to select a CC for transmitting data, control informationand/or the like. In addition, since a wider bandwidth involves largerintermodulation distortion, reducing the power allocation priority foran SRS having a wide bandwidth can reduce the influence of out-of-bandleakage (intermodulation distortion) over a wide range on a differentCC.

It is also possible to introduce a threshold into the bandwidthdetermination and to preferentially drop a corresponding SRS when abandwidth between SRSes or a difference between bandwidths of SRSesexceeds the threshold.

In addition, the larger the ratio of an SRS bandwidth to a CC bandwidth(e.g., SRS bandwidth/CC bandwidth) is, the more the power allocationpriority for the corresponding SRS on the CC may be lowered.

Meanwhile, when an SRS having a narrow bandwidth is preferentiallydropped over an SRS having a wide bandwidth, the following effects canbe obtained. When a high quality frequency resource is assigned bymeasuring a propagation channel over a wide bandwidth of only one CC, awide range frequency band can be measured at once.

It is also possible to introduce a threshold into the bandwidthdetermination and to drop a corresponding SRS when a bandwidth betweenSRSes or a difference between the bandwidths of the SRSes exceeds thethreshold.

In addition, the smaller the ratio of an SRS bandwidth to a CC bandwidth(e.g., SRS bandwidth/CC bandwidth) is, the more the power allocationpriority for the corresponding SRS on the CC may be lowered.

Power Scaling Method 11

In power scaling method 11, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 raises the powerallocation priority for the SRS on a CC on which UCI is triggered (to betriggered) by control information included in a physical layer controlchannel PDCCH (UL or DL grant) or control information reported (to bereported) via higher layer signaling, of the plurality of SRSes of theScells. For example, power scaling controlling section 109 raises thepower allocation priority for the SRS on a CC on which UCI such asaperiodic CSI is triggered. On the other hand, when a plurality of SRSesof Scells is present, power scaling controlling section 109 lowers(preferentially drops, reduces the transmission power, stopstransmission, or sets the transmission power to be equal to zero) thepower allocation priority for the SRS on a CC on which no UCI istriggered (no UCI has been triggered) by control information included ina physical layer control channel PDCCH (UL or DL grant) or controlinformation reported (to be reported) via higher layer signaling, of theplurality of SRSes. For example, power scaling controlling section 109lowers the power allocation priority for the SRS on a CC on which UCIsuch as aperiodic CSI is not triggered (has not been triggered) by anyUL grant.

FIG. 14 illustrates an overview of power scaling method 11. As in thecases described above, the SRSes are simultaneously transmitted on thetwo CCs (CC#0 and CC#2) in FIG. 14. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.When the total value of transmission power of the SRS channels of thetwo CCs transmitted as a plurality of CCs exceeds the UE-specificmaximum transmission power, the power allocation priority for the SRS ona CC on which UCI such as aperiodic CSI is triggered (to be triggered)by a UL grant is raised, of the two SRSes of the two Scells. FIG. 14illustrates a situation where UCI has been triggered on the Scell ofCC#2 in a previous subframe while no UCI has been triggered on CC#0.

Accordingly, the same effects as those obtained with power scalingmethods 1 and 3 can be obtained among a plurality of Scells (SCCs).

The priority for the Scell on which UCI has been triggered may be keptfor a certain period. Moreover, the priority for the Scell may be keptuntil UCI is triggered on a different CC. In addition, when there is aplurality of Scells on which UCI has been triggered, SRS power scalingmay be performed according to the latest trigger information. When thereis a plurality of Scells on which UCI has been triggered and also theUCI has been triggered at the same time, power scaling priority may bedetermined in accordance with UL CC ID numbers (in ascending ordescending order).

Power Scaling Method 12

In power scaling method 12, power scaling controlling section 109preferentially drops an SRS having a low PSD over an SRS having a highPSD (lowers the power allocation priority, reduces the transmissionpower, stops the transmission, or sets the transmission power to beequal to zero).

When a difference in PSD of SRS between CCs is large, theintermodulation distortion of the SRS on the CC having a higher PSD maybecome larger than a PSD of an SRS on a different CC. Thisintermodulation distortion cannot be removed by a transmission filter.Specifically, when the SRS is transmitted without removal of theintermodulation distortion, the eNB measures the communication qualityof the CC by the SRS affected by the intermodulation distortion. As aresult, correct scheduling or transmission power control cannot beperformed. With respect to this problem, transmission of only an SRShaving a high PSD, which is unlikely to be affected by theintermodulation distortion, allows an eNB to perform measurement on theCC with high accuracy.

FIG. 15 illustrates an overview of power scaling method 12. In FIG. 15,as in the cases described above, the SRSes are simultaneouslytransmitted on the two CCs (CC#0 and CC#1) in FIG. 15. According to thecontrol signal reported from the base station (via higher layersignaling), CC#0 and CC#1 are each configured as an Scell. In FIG. 15,the dotted line indicates harmonic distortion (intermodulationdistortion). Under this condition, an SRS having a low PSD that islikely to be affected by intermodulation distortion is dropped.

It should be noted that, a transmission power control parameter (PUSCHor SRS) related to calculating a PSD value may be used to determine theSRS to be dropped. Examples of the parameter includes a TPC commandaccumulation value, transport block size, offset parameter related to anMCS level (TF), SRS offset value with respect to PUSCH transmissionpower, and the number of bits per RE (TB size/the number of allocatedREs). When these values are high, the corresponding SRS has a higherPSD. Thus, the SRS to be dropped may be determined based on thesevalues. In addition, when the number of allocated resource elements(REs) or the number of allocated subcarriers is small, the correspondingSRS has a higher PSD. Thus, the SRS to be dropped may be determinedbased on these values.

In addition, it is also possible to introduce a threshold for PSDs orthe abovementioned parameters and to preferentially drop thecorresponding SRS when these values exceed the threshold.

As described above, according to Embodiment 1, when power scaling occursin simultaneous transmission of SRSes using a Pcell and Scell, thetransmission power is preferentially allocated with respect to the SRSof a Pcell over the SRS of an Scell. Thus, it is possible to reduce theprobability of a CC that transmits an SRS with low power allocationpriority being identical to a CC on which UCI is multiplexed.Accordingly, the propagation channel quality information on a Pcell onwhich UCI is likely to be multiplexed can be estimated with highaccuracy using an SRS having high power allocation priority, which inturn allows an eNB to indicate appropriate transmission power for asubsequent UL channel on which UCI is transmitted.

It should be noted that, although a description has been given regardingthe situation between CCs, the methods described above may be applied toa plurality of SRSes on a CC.

In addition, the power scaling methods described above may be used incombination.

Moreover, the methods that have been described with an assumption thatthey are applied to a plurality of SRSes on a plurality of Scells may beapplied in the same manner when a plurality of SRSes on Pcell or aplurality of SRSes on a plurality of Pcells is present.

Furthermore, as a method of reducing the transmission power of an SRSwith low power allocation priority, an SRS scaling weight reported froman eNB to a terminal (via higher layer signaling) may be used to reducethe transmission power.

When w_Pcell_SRS and w_Scell_SRS are defined as the scaling weightsapplied to SRSes of a Pcell and Scell respectively, the scaling weightsmay be set (defined) to satisfy w_Pcell_SRS>w_Scell_SRS. Alternatively,the scaling weights may be defined to satisfy w_Pcell_SRS=1, andw_Scell_SRS<1.

In addition, although a description has been given regarding prioritybetween a plurality (periodic or aperiodic) SRSes when power scalingoccurs, the method to be described below may be used for powerallocation priority between an (periodic or aperiodic) SRS and anotherUL channel (such as PUCCH or PUSCH).

Power Scaling Method 13

In power scaling method 13, simultaneous transmission of an (periodic oraperiodic) SRS and a PUCCH is performed using only one CC having abandwidth of 20 MHz or the like in Release 8 LTE. For simultaneoustransmission of an (periodic or aperiodic) SRS and a PUCCH on one CC, inorder to avoid an increase in peak-to-average power ratio (PAPR) of thetransmission signal (multi-carrier transmission), a PUCCH in a shortenedformat not transmitting the last SC-FDMA symbol of one subframe by ratematching is used for the PUCCH, and only a periodic SRS is transmittedon the last SC-FDMA symbol of one subframe (see, FIG. 16).

Meanwhile, studies have been carried out on introducing simultaneoustransmission on a plurality of CCs including a CC transmitting a PUCCHand a CC transmitting an SRS into LTE-A, which uses a plurality of CCs.Accordingly, power scaling needs to be performed when the transmissionpower exceeds the UE-specific maximum transmission power in simultaneoustransmission of a PUCCH and an SRS on CCs using the last SC-FDMA symbolof one subframe. Stated differently, it is necessary to determine powerallocation priority for the PUCCH and SRS.

NPL 1 discloses the following priority used when power scaling occurs.

-   -   PUCCH>SRS>PUSCH

NPL 1, however, has the following problems when an (periodic oraperiodic) SRS and a PUCCH are simultaneously transmitted. Specifically,as described above, when the transmission power of an SRS is reduced(halfway) so as to satisfy the requirement with respect to theUE-specific maximum transmission power on the basis of the rule thatindicates the power allocation priority for the transmission power of anSRS is lower than the transmission power of a PUCCH, the eNB does nothave any information indicating when power scaling has occurred in aterminal and/or the like, basically. For this reason, the eNBerroneously recognizes the reason for reduction in the SRS receptionlevel as being deterioration in the quality of the mobile communicationchannel, which easily changes with time, instead of the occurrence ofpower scaling in the terminal. In addition, the eNB reports aninstruction to use a large transmission power value (small MCS value)not less than a value required to satisfy predetermined receptionquality for subsequent transmission of a UL channel (on which UCI ismultiplexed) such as a PUSCH. Stated differently, transmission of a ULchannel is performed with excessive quality during transmission of asubsequent UL channel such as a PUSCH in this case (co-channelinterference to another cell is increased when an instruction toincrease the transmission power is transmitted. In addition, anotherproblem such as an unnecessary increase in the power consumption of theterminal is caused).

In this respect, in a power scaling method used in simultaneoustransmission of an (periodic/aperiodic) SRS and a PUCCH, power scalingcontrolling section 109 performs power scaling by keeping (not changing)the transmission power of a PUCCH on a Pcell, and dropping (stopping thetransmission or setting the transmission power to be equal to zero) anSRS of an Scell.

FIG. 17 illustrates an overview of power scaling method 13. In FIG. 17,a PUCCH on CC#1 and an SRS on CC#2 are simultaneously transmitted whileno transmission is performed on CC#0. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 17 illustrates the operation to perform power scaling by keeping(i.e., not changing) the transmission power of the PUCCH on CC#1configured as a Pcell, and dropping the SRS on CC#2 configured as anScell, when the total value of transmission power of the PUCCH and theSRS channel transmitted on the plurality of CCs exceeds the UE-specificmaximum transmission power in this situation.

FIG. 18 illustrates a configuration of a transmitter used insimultaneous transmission of a PUCCH and an SRS on different CCs. InFIG. 18, coding and modulation section 110-1 receives, as input, controlinformation (such as ACK/NACK or CQI) transmitted on a PUCCH andperforms the processing similar to that described in the embodiment. Thetransmission power of the PUCCH is set in transmission power configuringsection 112-1 on the basis of the information received from powerscaling controlling section 109. The processing performed hereinafter isthe same as that described above (see, FIG. 2). Thus, the description ofthe processing is omitted herein. Meanwhile, for the CC on which the SRSis transmitted, transmission power configuring section 112-1 receivesthe SRS, and sets the transmission power of the SRS on the basis of theinformation received from power scaling controlling section 109.

Accordingly, dropping the SRS of an Scell enables simplification ofcomplex power allocation control between CCs in addition to obtainingthe effects brought about by power scaling method 3. In addition, theman hours for testing can be reduced in the same manner described above.

In addition, when a UE miss-detects trigger information on an aperiodicSRS, which is newly introduced into LTE-A and is reported on a physicallayer control channel PDCCH, the UE transmits no SRS (transmission powerfor the corresponding CC (resource)=0). More specifically, it ispossible to configure UEs to perform the equivalent operation when powerscaling occurs and when miss-detection of a UE occurs (forsimplification). Accordingly, it is made possible for an eNB to support,by a single operation, the cases where power scaling occurs and wheremiss-detection of a UE occurs. For example, when an eNB can measure onlya reception SRS level equal to a noise level during an SRS receptionperiod in blind-detection processing of SRS receiving power in the eNB,the eNB can support both of the abovementioned cases by the singleoperation, which is to instruct the terminal to retransmit (trigger) anSRS with an appropriate transmission power value for the SRS again.

It should be noted that, when a plurality of SRSes is present on aplurality of Scells, all the SRSes of the Scells may be dropped.Furthermore, the power scaling methods used when a plurality of SRSes ispresent on a plurality of Scells may be used.

Although a description has been given regarding the case where powerscaling occurs in simultaneous transmission of an SRS and a PUCCH, it ispossible to transmit an SRS and a PUCCH on a plurality of CCs when nopower scaling occurs.

Power Scaling Method 14

In power scaling method 14, simultaneous transmission of an (periodic oraperiodic) SRS and a PUSCH is performed using only one CC having abandwidth of 20 MHz or the like in Release 8 LTE. For simultaneoustransmission of an (periodic or aperiodic) SRS and a PUSCH on one CC, inorder to avoid an increase in peak-to-average power ratio (PAPR) of thetransmission signal (multi-carrier transmission), a PUSCH in a shortenedformat not transmitting the last SC-FDMA symbol of one subframe by ratematching (puncturing) is used for the PUSCH, and only a periodic SRS istransmitted on the last SC-FDMA symbol of one subframe (see, FIG. 19).

Meanwhile, studies have been carried out on introducing simultaneoustransmission on a plurality of CCs including a CC transmitting a PUSCHand a CC transmitting an SRS into LTE-A, which uses a plurality of CCs.Accordingly, power scaling needs to be performed when the transmissionpower exceeds the UE-specific maximum transmission power in simultaneoustransmission of a PUSCH and an SRS on CCs using the last SC-FDMA symbolof one subframe. Stated differently, it is necessary to determine powerallocation priority for the PUCCH and SRS.

As described above, NPL 1 discloses the following priority used whenpower scaling occurs.

-   -   PUCCH>SRS>PUSCH

NPL 1, however, has the following problems when an (periodic oraperiodic) SRS and a PUSCH are simultaneously transmitted. Specifically,as described above, when the transmission power of a PUSCH is reduced(halfway) so as to satisfy the requirement with respect to theUE-specific maximum transmission power on the basis of the rule thatindicates the power allocation priority for the transmission power of aPUSCH is lower than the transmission power of an SRS, the probabilitythat the eNB cannot correctly receive multiple amplitude shift keyingsubjected to power scaling is increased when multiple amplitude shiftkeying such as 16QAM or 64QAM is used on data transmitted on the PUSCH(or control information). For example, the probability is increased thatthe modulation accuracy and error vector magnitude (EVM) of themultilevel modulation signal subjected to power scaling no longersatisfy a predetermined condition at the time of transmission due topower scaling. In addition, although the information on multipleamplitude shift keying such as 16QAM is indicated by amplitude (squareroot of power), the eNB basically has no information indicating whenpower scaling has occurred in a terminal and/or the like, for example.Accordingly, the eNB demodulates and decodes the signal with anassumption that no power scaling is applied to the PUSCH. Thus, theprobability of the eNB not correctly receiving the signal is increased.

In this respect, in power scaling method 14 used in simultaneoustransmission of a (periodic/aperiodic) SRS and a PUSCH, power scalingcontrolling section 109 performs power scaling by keeping (not changing)the transmission power of the PUSCH, and dropping (stopping thetransmission or setting the transmission power to be equal to zero) thetransmission power of the SRS (of Scell).

Accordingly, dropping the SRS of an Scell enables simplification ofcomplex power allocation control between CCs in addition to obtainingthe effects similar to those brought about by power scaling method 3. Inaddition, the man hours for testing can be reduced in the same mannerdescribed above.

Moreover, it is possible to avoid the abovementioned problems with aPUSCH and also to increase the probability of multiple amplitude shiftkeying such as 16QAM, being correctly transmitted.

FIG. 20 illustrates an overview of power scaling method 14. In FIG. 20,a PUCCH (with UCI) on CC#1 and an SRS on CC#2 are simultaneouslytransmitted while no transmission is performed on CC#0. According to thecontrol signal reported from the base station (via higher layersignaling), CC#0, CC#1, and CC#2 are configured as an Scell, Pcell, andScell, respectively. FIG. 20 illustrates the operation to perform powerscaling by keeping (i.e., not changing) the transmission power of thePUSCH (with UCI) on CC#1, and dropping the SRS on CC#2 configured as anScell, when the total value of transmission power of the PUSCH (withUCI) and the SRS channel transmitted on a plurality of CCs exceeds theUE-specific maximum transmission power in this situation.

It is favorable to use power scaling method 14 as a power scaling methodused when UCI is multiplexed on a PUSCH, i.e., when a PUSCH on which UCIis multiplexed and a (periodic or aperiodic) SRS are simultaneouslytransmitted. Accordingly, the probability that the UCI which has highpriority and to which no retransmission is applied is correctlytransmitted to an eNB can be increased.

Power Scaling Method 15

When no UCI is multiplexed on a PUSCH, power scaling controlling section109 may perform power scaling by keeping (i.e., not changing) thetransmission power of the SRS, and dropping (stopping the transmissionor setting the transmission power to be equal to zero) the transmissionpower of the PUSCH as power scaling method 15 used for the situationopposite to that of power scaling method 14 and used when an (periodicor aperiodic) SRS and a PUSCH are simultaneously transmitted. Thepriority for an SRS with respect to a PUSCH on which no UCI ismultiplexed, i.e., PUSCH without UCI to which retransmission is appliedcan be raised. Thus, the measurement accuracy using an SRS can beincreased as in the case of power scaling method 3 while simple powerallocation processing is performed between CCs.

FIG. 21 illustrates an overview of power scaling method 15. In FIG. 21,an SRS on CC#1 and a PUCCH (without UCI) on CC#2 are simultaneouslytransmitted while no transmission is performed on CC#0. According to thecontrol signal reported from the base station (via higher layersignaling), CC#0, CC#1, and CC#2 are configured as an Scell, Pcell, andScell, respectively. FIG. 21 illustrates the operation to perform powerscaling by keeping (i.e., not changing) the transmission power of theSRS on CC#1, and dropping the PUSCH (without UCI) on CC#2 configured asan Scell, when the total value of transmission power of the PUSCH(without UCI) and the SRS channel transmitted on a plurality of CCsexceeds the UE-specific maximum transmission power in this situation.

It should be noted that, power scaling methods 14 and 15 may beselectively used in such a way that power scaling method 14 is used whena (periodic or aperiodic) SRS and a PUSCH on which UCI is multiplexedare simultaneously transmitted, and power scaling method 15 is used whena (periodic or aperiodic) SRS and a PUSCH on which no UCI is multiplexedare simultaneously transmitted. In other words, as illustrated in FIG.20, power scaling method 14 is used when a PUSCH with UCI is transmittedusing a Pcell and an SRS is transmitted using an Scell, while powerscaling method 15 is used when an SRS is transmitted using a Pcell and aPUSCH without UCI is transmitted using an Scell. Thus, the measurementaccuracy using an SRS can be increased as in the case of power scalingmethod 3 while high quality UCI transmission is maintained.

Although the description has been given of the case where power scalingoccurs in simultaneous transmission of an SRS and a PUSCH, an SRS and aPUSCH may be transmitted on a plurality of CCs when no power scalingoccurs.

In addition, the power scaling methods described above may be used incombination.

Embodiment 2

Embodiment 1 has been described with respect to the power scalingmethods used when the total value of transmission power of a pluralityof uplink channels transmitted on a plurality of CCs (cells) exceeds theUE-specific maximum transmission power in simultaneous transmission ofthe plurality of uplink channels (such as SRS, PUSCH and PUCCH).However, all the power scaling methods described in Embodiment 1 may beused when the total value of transmission power of a plurality of uplinkchannels transmitted on a plurality of CCs (cells) does not exceed theUE-specific maximum transmission power, but simultaneous transmission ofa plurality of uplink channels (such as simultaneous transmission ofSRSes, simultaneous transmission of an SRS and a PUSCH and simultaneoustransmission of an SRS and a PUCCH) on a plurality of cells (e.g., aPcell and a plurality of Scells) or a plurality of CCs (e.g., a PCC anda plurality of SCCs) occurs.

In Embodiment 2, a detailed description will be provided regarding thepower scaling methods described in Embodiment 1 used when simultaneoustransmission of a plurality of uplink channels (such as simultaneoustransmission of SRSes, simultaneous transmission of an SRS and a PUSCHand simultaneous transmission of an SRS and a PUCCH) on a plurality ofcells (e.g., a Pcell and a plurality of Scells) or a plurality of CCs(e.g., a PCC and a plurality of SCCs) occurs.

First, the background of Embodiment 2 will be briefly described.

Implementation of a plurality of power amplifiers (PAs) on a terminalusing a single amplifier for each UL channel for the purpose ofamplifying transmission signals on a plurality of UL channels from theterminal causes an increase in the cost of the terminal and also hindersminiaturization of the terminal (increases the size of the terminal).For this reason, a method in which a single PA covers a plurality of ULchannels (CC, cell, carrier wave, frequency band, and/or the like),i.e., amplifies the transmission signals of the plurality of UL channelsby the single PA is also used as an implementation method for terminals.In this case, a large peak-to-average power ratio (PAPR) of thesimultaneous transmission (multi-carrier transmission) signals of aplurality of UL channels has a large influence on the PA havingnon-linearity as the input and output characteristics of the power(voltage). For example, the power efficiency of the PA is degraded.Otherwise, large non-linearity distortion occurs in the amplifiedsignal. In particular, a terminal near a cell edge that needs largetransmission power and has no margin for the transmission power (powerhead room (PHR) value is small) is significantly affected.

For this reason, in order to mitigate the influence from thetransmission signals of a plurality of UL channels on a PA (in order toavoid any increase in PAPR of the transmission signals) in simultaneoustransmission of a plurality of UL channels, a method is used, whichreduces transmission power of a certain UL channel of the plurality ofUL channels or sets a UL channel that is not transmitted. Specifically,power scaling is applied to a plurality of UL channels when simultaneoustransmission of a plurality of uplink channels (such as simultaneoustransmission of SRSes, simultaneous transmission of an SRS and a PUSCHand simultaneous transmission of an SRS and a PUCCH) on a plurality ofcells (e.g., a Pcell and a plurality of Scells) or a plurality of CCs(e.g., a PCC and a plurality of SCCs) occurs.

Accordingly, problems similar to those described in Embodiment 1 occurwhen simultaneous transmission of a plurality of uplink channels occurson a plurality of cells or CCs although the total value of transmissionpower of the plurality of uplink channels transmitted on the pluralityof CCs (cells) does not exceed the UE-specific maximum transmissionpower. Stated differently, the technique disclosed in NPL 1 has thefollowing problems. Specifically, the technique does not take intoaccount the effects of the method of selecting a CC for multiplexingimportant UCI to which no retransmission is applied, on the powerallocation priority used when power scaling is applied in simultaneoustransmission of a plurality of periodic SRSes on a plurality of CCs.Since UCI needs to be reported to an eNB from a terminal with a smalldelay, only single transmission is supported for UCI.

Accordingly, when a CC configured with lower power allocation prioritybased on the technique disclosed in NPL 1 (CC that is likely to have alarger CQI measurement error (measurement accuracy is degraded) in theeNB) is used as a CC on which UCI is to be multiplexed, the measurementerror of communication quality (e.g., Signal-to-Interference plus Noisepower Ratio (SINR)) on the CC, which is derived using an SRS subjectedto power scaling (transmission power is reduced), is large. Accordingly,the eNB cannot report an appropriate transmission power (or Modulationand channel Coding Scheme (MCS)) value for the UCI to be transmitted ina subsequent subframe.

For example, when a UE performs power scaling (reduction of transmissionpower) for an SRS on a certain CC of a smaller UL CC ID number based onthe technique disclosed in NPL 1 in simultaneous transmission of aplurality of SRSes on a plurality of CCs, the eNB measures thecommunication quality of the CC using a received SRS with a reducedreception level.

However, the eNB may erroneously recognize the reason for reduction inthe SRS reception level as being deterioration in the quality of themobile communication channel, which easily changes with time, instead ofthe occurrence of power scaling in the terminal. In addition, when powerscaling (reduction in transmission power) is performed on the SRS withtransmission power that is correctly controlled by transmission powercontrol for each UL channel so as to satisfy a predetermined requirementvalue necessary for reception quality measurement, the transmissionpower no longer satisfies the requirement.

Accordingly, the eNB instructs, by using a falsely recognizedcommunication quality measurement value or a communication qualitymeasurement value obtained from the received SRS that does not satisfy apredetermined requirement value, a terminal to use a larger transmissionpower value (small MCS value) not less than a value required to satisfypredetermined reception quality for transmission of a subsequent ULchannel such as a PUSCH. Stated differently, transmission of a ULchannel with excessive quality is performed for a subsequent UL channelsuch as a PUSCH in this case (co-channel interference to another cell isincreased when an instruction to increase the transmission power istransmitted. In addition, another problem such as an unnecessaryincrease in the power consumption of the terminal is caused). Inparticular, when the eNB reports an inappropriate transmission powervalue (MCS value) for a PUSCH or PUCCH on which important UCI ismultiplexed, by using the communication quality measurement valueobtained from the received SRS that does not satisfy a predeterminedrequirement value, the system control is significantly affected since noretransmission is applied to UCI.

More specifically, the same problems as those described in Embodiment 1occur. Accordingly, the invention of a power scaling method similar tothat in Embodiment 1 has been made with careful observation of theabovementioned points in Embodiment 2 as well.

Hereinafter, a description will be provided regarding a configurationand processing of terminal 100 of Embodiment 2 with reference to FIG. 2.This description will focus on differences between Embodiment 1 andEmbodiment 2.

The series of processes up to control information extraction section 106is similar to the processes performed in Embodiment 1. Controlinformation extraction section 106 extracts control information from thesignal outputted from channel decoding section 105 and outputs theextracted control information to transmission power calculating section107. The control information to be extracted herein includes: UL grantinformation (allocation bandwidth, MCS set, PUSCH, SRS or PUCCHtransmission power information (TPC command, transmission formatdependent value Δ_(TF) such as MCS, and SRS offset value P_(SRS) _(_)_(offset)), and aperiodic SRS trigger information, for example), DLgrant information (transmission power information on PUCCH or the like,and aperiodic SRS trigger information, for example), UCI request(trigger) information, CC/cell information such as Pcell/Scell andPCC/SCC.

Transmission power calculating section 107 calculates transmission powerof a plurality of UL channels (on each CC) using the control informationoutputted from control information extraction section 106, CC-specific(each UL channel) maximum transmission power (such as power class ofpower amplifier (PA) and MPR), path-loss (estimate) information,transmission power related reporting information on a higher layer(path-loss compensation coefficient, P_o (target reception level value)and/or the like), for example. As a specific calculation method, PUSCH,PUCCH and SRS transmission power calculation formulae described in NPL 3are used, for example. Transmission power calculating section 107outputs transmission power values of a plurality of UL channels (on eachCC) to power scaling detecting section 108 and power scaling controllingsection 109.

Power scaling detecting section 108 detects whether or not there is morethan one UL channel transmission power value outputted from transmissionpower calculating section 107 (detects whether or not simultaneoustransmission of a plurality of UL channels occurs). When there is notmore than one UL channel transmission power value (one), power scalingdetecting section 108 outputs control information indicating “powerscaling is unnecessary” to power scaling controlling section 109. Whenthere is more than one UL channel transmission power value, on the otherhand, power scaling detecting section 108 outputs control informationindicating “power scaling is necessary” to power scaling controllingsection 109.

In accordance with information indicating the presence or absence ofoccurrence of power scaling outputted from power scaling detectingsection 108, power scaling controlling section 109 performs transmissionpower scaling on each UL channel (such as SRS, PUSCH and PUCCH) when thecontrol information indicates “power scaling is necessary,” to determinethe transmission power for each of the plurality of UL channels (CCs).The transmission power information obtained after power scaling isoutputted to transmission power setting sections 112-1 to 112-N. Thedetails of an SRS power scaling method will be described hereinafter.

The series of processes from coding and modulation sections 110-1 to110-N to radio transmission processing section 115 is the same as thatin Embodiment 1 (see, FIG. 2). Thus, the description of the processes isomitted herein. For the CC on which an SRS is transmitted, transmissionpower setting sections 112-1 to 112-N receive an SRS, and transmissionpower of the SRSes are set based on the information received from powerscaling controlling section 109.

Power scaling methods 1-A to 12-A for SRSes in simultaneous transmissionof a plurality of SRSes will be described.

Power Scaling Method 1-A

In power scaling method 1-A, transmission power calculating section 107calculates transmission power of a plurality of UL channels on aplurality of CCs, first.

Next, power scaling detecting section 108 detects whether or not thereis a plurality of transmission power values of UL channels transmittedon a plurality of CCs (detects whether or not simultaneous transmissionof a plurality of UL channels occurs). More specifically, power scalingdetecting section 108 detects whether or not power scaling occurs.

Next, when power scaling (simultaneous transmission of a plurality of ULchannels) occurs in simultaneous transmission of a plurality of(periodic or aperiodic) SRSes using a Pcell (PCC) and Scell (SCC), powerscaling controlling section 109 preferentially allocates transmissionpower with respect to an SRS of a Pcell over an SRS of an Scell of theplurality of (periodic or aperiodic) SRSes to be transmittedsimultaneously.

FIG. 4 illustrates an overview of power scaling method 1-A. In FIG. 4,the SRSes are simultaneously transmitted on three CCs (CC#0 to CC#2).For example, the last symbol position of one subframe is used totransmit only the SRS on the three CCs (see, FIG. 3). According to thecontrol signal reported from the base station (via higher layersignaling), CC#0, CC#1, and CC#2 are configured as an Scell, Pcell, andScell, respectively. FIG. 4 illustrates the operation to preferentiallyallocate transmission power with respect to the SRS on CC#1 configuredas a Pcell over the SRSes on CC#0 and CC#2 each configured as an Scell,when there is a plurality of transmission power values of SRS channelstransmitted on the three CCs including a Pcell and an Scell (whensimultaneous transmission of a plurality of SRS channels occurs) in thissituation.

Accordingly, it is possible to reduce the probability of a CC thattransmits an SRS with low power allocation priority (i.e., CC that islikely to have a larger CQI measurement error) being identical to a CCon which UCI is to be multiplexed. For example, the probability of theScells of CC#0 and CC#2 with low power allocation priority beingidentical to a CC on which UCI is to be multiplexed can be reduced asillustrated in FIG. 4.

Thus, the propagation channel quality information (Channel QualityIndicator (CQI)) on the Pcell on which UCI is likely to be multiplexedcan be estimated with high accuracy by the SRS with high powerallocation priority. Accordingly, the eNB can indicate appropriatetransmission power (MCS) for a subsequent UL channel transmitting UCI(e.g., PUSCH on which data and UCI are multiplexed, PUCCH on which UCIis multiplexed, and/or the like). Stated differently, it is possible totransmit UCI without setting excessive quality for the transmissionformat used for the UL channel transmitting the UCI. In addition,transmission can be performed without any unnecessary increase of theco-channel interference to another cell or in power consumption of theterminal. In other words, the eNB can report, by using a communicationquality measurement value obtained from a received SRS of Pcell, whichsatisfies a predetermined requirement value, an appropriate transmissionpower value (MCS value) for a PUSCH or PUCCH on which important UCI ismultiplexed, and thus allows UCI to which no retransmission is appliedto be correctly transmitted.

Power Scaling Method 2-A

In power scaling method 2-A, power scaling controlling section 109performs power scaling by setting the transmission power of the SRS of aPcell to be not greater than the CC-specific (for each UL channel)maximum transmission power (while satisfying the CC-specific maximumtransmission power condition), then keeping (not changing) thetransmission power of the SRS of the Pcell, and reducing thetransmission power of an Scell.

FIG. 5 illustrates an overview of power scaling method 2-A. In FIG. 5,the SRSes are simultaneously transmitted on three CCs (CC#0 to CC#2).According to the control signal reported from the base station (viahigher layer signaling), CC#0, CC#1, and CC#2 are configured as anScell, Pcell, and Scell, respectively. FIG. 5 illustrates the operationto perform power scaling by keeping (i.e., not changing) thetransmission power of the SRS on CC#1 configured as Pcell and reducingthe transmission power of the SRSes on CC#0 and CC#2 each configured asan Scell, when there is a plurality of transmission power values of SRSchannels transmitted on the three CCs including a Pcell and an Scell(when simultaneous transmission of a plurality of SRS channels occurs)in this situation.

Accordingly, setting the transmission power of the SRS of a Pcellconfigured for each terminal, in such a way that the condition that thetransmission power of the SRS of a Pcell is equal to or less than themaximum transmission power of each CC (each UL channel) makes itpossible to maintain co-channel interference to another cell from a CCconfigured as a Pcell used preferentially, to be equal to or less than acertain predetermined value and also makes scheduling for each CC andcross-carrier scheduling performed by each eNB easier. In addition,surely keeping (not allowing any change) the transmission power level ofthe SRS of a Pcell allows the propagation channel quality of the Pcellby a (periodic or aperiodic) SRS to be measured with even higheraccuracy than that in the case of power scaling method 1-A.

In other words, it is possible to prevent the communication qualityinformation on a Pcell that is obtained from the received SRS of thePcell from being affected by power scaling in the terminal (to avoidmisrecognition of the UE transmission power between the UE and eNB, orenables use of a communication quality measurement value obtained fromthe received SRS that satisfies a predetermined requirement value).Thus, the eNB can perform more appropriate operation in subsequentscheduling (resource allocation) and transmission power (AdaptiveModulation channel Coding (AMC)) control on the Pcell on which UCI islikely to be transmitted. Accordingly, it is possible to obtain theeffect of eliminating the need for passive control such as setting alarge margin for transmission power (AMC) control.

Power Scaling Method 3-A

In power scaling method 3-A, power scaling controlling section 109performs power scaling by keeping (not changing) the transmission powerof the SRS of a Pcell, and dropping the SRS of an Scell (this means thatno SRS is transmitted or transmission power is set equal to zero(transmission power=0)).

FIG. 6 illustrates an overview of power scaling method 3-A. As in FIGS.4 and 5, the SRSes are simultaneously transmitted on three CCs (CC#0 toCC#2) in FIG. 6. According to the control signal reported from the basestation (via higher layer signaling), CC#0, CC#1, and CC#2 areconfigured as an Scell, Pcell, and Scell, respectively. FIG. 6illustrates the operation to perform power scaling by keeping (i.e., notchanging) the transmission power of the SRS on CC#1 configured as aPcell, and dropping the SRS on CC#2 configured as an Scell, when thereis a plurality of transmission power values of SRS channels transmittedon the three CCs including a Pcell and an Scell (when simultaneoustransmission of a plurality of SRS channels occurs) in this situation.

Accordingly, dropping the SRS of an Scell enables simplification ofcomplex power allocation control between CCs in addition to obtainingthe effects brought about by power scaling method 1-A. In LTE-A, an SRSis multiplexed only at the last symbol of one subframe consisting of 14symbols. Accordingly, even when the last symbol alone is dropped, theinfluence on the spectrum efficiency is small. For example, when an SRSis transmitted only on one CC, the impact of dropping the symbol isequal to 7% ( 1/14=7%). Moreover, the frequency (cycle) of SRStransmission is, for example, once in 10 ms for periodic SRS, which isvery low as compared with the frequency of data transmission. Thus, theinfluence on the spectrum efficiency is even smaller (data can betransmitted once in 1 ms at minimum).

In addition, dropping an SRS enables a reduction in the possibility thatthe eNB erroneously recognizes that the quality of the propagationchannel has been deteriorated and also avoiding unnecessary transmissionof the SRS which no longer satisfies a predetermined requirement valuefor reception quality measurement (to which scaling has been applied).In other words, unnecessary power consumption of terminals can bereduced.

In Embodiment 2, all the SRSes of a plurality of Scells may be droppeduniformly. FIG. 7 illustrates a case where two SRSes respectively onCC#0 and CC#2 are dropped in simultaneous transmission of SRSes on CC#0to CC#2. Thus, it is possible to omit the arithmetic operation requiredfor power allocation processing between CCs while obtaining the sameeffects as those described above, and also to significantly reduce theman hours for testing terminals (or eNBs) with respect to power scaling,which is indispensable for the commercialization of LTE-A. In addition,unnecessary power consumption of terminals can be further reduced.

In addition, when a periodic SRS and aperiodic SRS are transmitted usingScells, a periodic SRS may be preferentially dropped over an aperiodicSRS.

An aperiodic SRS is the SRS that is newly introduced into LTE-A andconfigured to be triggered by a PDCCH, which is a physical layerdownlink control channel, for an eNB to measure new quality informationwith low delay. Meanwhile, a periodic SRS (of transmission cycle,trigger, timer and/or the like) is configured by higher layer signaling,so that only low speed control is possible. Accordingly, the feature ofan aperiodic SRS (for eNB to make immediate determination on CQImeasurement using SRS) can be reflected in power scaling processing, andthe same effects as those described above can be obtained.

FIG. 8 illustrates how the periodic SRS of the Scell of CC#2 is droppedwhen the aperiodic SRS is triggered on the Scell of CC#0 and theperiodic SRS is triggered on the Scell of CC#2 while nothing istransmitted using the Pcell of CC#1 at the same symbol position of thesame subframe (e.g., the last symbol position of a subframe).

Power Scaling Method 4-A

In power scaling method 4-A, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 reduces (drops or setsthe transmission power to be equal to zero (no SRS transmission)) thetransmission power in ascending order of the transmission power of SRSesof the Scells (or the smallest) (while keeping the transmission power ofthe SRS of the Pcell).

FIG. 9 illustrates an overview of power scaling method 4-A. As in FIGS.4 and 5, the SRSes are simultaneously transmitted on the three CCs (CC#0to CC#2) in FIG. 9. According to the control signal reported from thebase station (via higher layer signaling), CC#0, CC#1, and CC#2 areconfigured as an Scell, Pcell, and Scell, respectively. In addition, thetransmission power of the SRS of the Scell before power scaling islarger for the SRS on CC#2 than for the SRS on CC#0. FIG. 9 illustratesthe operation to perform power scaling by preferentially dropping theSRS transmission on CC#0 configured as the Scell with smallertransmission power (or the smallest) when there is a plurality oftransmission power values of SRS channels transmitted on the three CCsincluding a Pcell and an Scell (when simultaneous transmission of aplurality of SRS channels occurs) in this situation.

Accordingly, since an SRS with smaller transmission power is more likelyto fall below an SRS detection level capable of being received by an eNB(e.g., noise level at eNB), preferentially reducing the transmissionpower of the SRS of an Scell with smaller transmission power makes itpossible to maintain the accuracy in measurement using the SRS of theScell from which no transmission power is reduced, while maintaininghighly accurate quality measurement on a Pcell.

Power Scaling Method 5-A

In power scaling method 5-A, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 uniformly reduces thetransmission power of the plurality of SRSes of the Scells (reduces thesame transmission power value or applies the same scaling (weighting))(while keeping (not changing) the transmission power of the SRS of aPcell).

FIG. 10 illustrates an overview of power scaling method 5-A. As in thecase described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 10. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 10 illustrates how the transmission power of CC#0 and CC#2configured as the Scells is uniformly reduced when there is a pluralityof transmission power values of SRS channels transmitted on the threeCCs including a Pcell and an Scell (when simultaneous transmission of aplurality of SRS channels occurs) in this situation. Examples of themethod used to uniformly reduce the transmission power include a methodto reduce transmission power with the same value (true value or decibelvalue) or to apply the same scaling (weight) (applied in LTE-A).Meanwhile, as the scaling weight used for reducing the transmissionpower of SRSes, a scaling weight for SRSes may be used, or the samescaling weight as that for another UL channel (e.g., PUSCH, PUSCH withUCI or PUSCH without UCI) may be used for SRSes. The term “scalingweight” used herein refers to a parameter that is previously reported toa terminal from an eNB.

Accordingly, it is possible to enable simplification of complex powerallocation control between CCs while maintaining highly accurate qualitymeasurement on a Pcell.

Power Scaling Method 6-A

In power scaling method 6-A, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 drops all the SRSes ofthe Scells (uniformly drops SRSes of Scells) (stops the transmission orsets the transmission power to be equal to zero).

FIG. 11 illustrates an overview of power scaling method 6-A. As in thecase described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 11. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 11 illustrates how the SRSes on CC#0 and CC#2 configured as theScells are uniformly dropped when there is a plurality of transmissionpower values of SRS channels transmitted on the three CCs including aPcell and an Scell (when simultaneous transmission of a plurality of SRSchannels occurs) in this situation.

Accordingly, it is possible to enable simplification of complex powerallocation control between CCs while obtaining the effects similar tothose obtained with power scaling method 3-A. In addition, the man hoursfor testing terminals (or eNBs) with respect to power scaling, which isindispensable for the commercialization of LTE can be significantlyreduced. For example, although it is required to determine thespecifications for testing all combinations of SRSes on a plurality ofScells to be transmitted, the man hours for the testing itself or fordetermining the specifications for the testing can be reduced.Furthermore, unnecessary power consumption of terminals can be reduced.

It should be noted that, when a plurality of SRSes is present in Scells,instead of uniformly dropping all the SRSes, it is possible to drop theSRSes in (ascending/descending) order of the CC (cell) numbers.

Power Scaling Method 7-A

In power scaling method 7-A, when transmission power of a certain SRS ofa plurality of SRSes is smaller than the SRS having the largesttransmission power among the SRSes by at least the amount of apredetermined threshold, power scaling controlling section 109 reducesthe transmission power of the certain SRS of the Scell or drops thecertain SRS (stops the transmission or sets the transmission power to beequal to zero).

FIG. 12 illustrates an overview of power scaling method 7-A. As in thecases described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 12. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 12 illustrates how the SRS of the Scell is dropped when there is aplurality of transmission power values of SRS channels transmitted onthe three CCs (when simultaneous transmission of a plurality of SRSchannels occurs) and also when a difference between the transmissionpower of the SRS having the largest transmission power among theplurality of SRSes and the SRS of the Scell is at least a predeterminedthreshold in this situation described above. FIG. 12 illustrates a casewhere the difference between the transmission power of the SRS of theScell of CC#2 and the transmission power of the SRS of the Pcell ofCC#1, which is the largest among the plurality of SRSes, is at least apredetermined value.

When a difference in the transmission power of SRS between CCs is large,there occurs a situation where the intermodulation distortion of the SRSon the CC with larger transmission power becomes larger than thetransmission power of the SRS on a different CC. The intermodulationdistortion cannot be removed by a transmission filter. In other words,when the SRS is transmitted without removal of the intermodulationdistortion, the eNB measures the communication quality of the CC by theSRS affected by the intermodulation distortion. As a result, correctscheduling or transmission power control cannot be performed.Accordingly, this problem can be avoided by dropping the SRS of theScell when the difference between the largest SRS transmission power andthe SRS transmission power of the Scell is at least a predeterminedthreshold.

As a method of setting the threshold, it is possible to set a certainvalue and to adaptively change the value according to a path-loss(measurement) value.

In addition, instead of the transmission power of an SRS having thelargest transmission power among a plurality of SRSes, the transmissionpower of a channel having the largest transmission power among ULchannels to be simultaneously transmitted may be set as the referencevalue. Accordingly, the same effects can be obtained with thisconfiguration.

Power Scaling Method 8-A

In power scaling method 8-A, when transmission power of a certain SRS ofan Scell is not greater than a predetermined threshold, power scalingcontrolling section 109 reduces the transmission power of the SRS of theScell or drops the SRS (stops the transmission or sets the transmissionpower to be equal to zero).

FIG. 13 illustrates an overview of power scaling method 8-A. As in thecases described above, the SRSes are simultaneously transmitted on thethree CCs (CC#0 to CC#2) in FIG. 13. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.FIG. 13 illustrates how the SRS of the Scell is dropped when there is aplurality of transmission power values of SRS channels transmitted onthe three CCs (when simultaneous transmission of a plurality of SRSchannels occurs) and also when the transmission power of the Scell ofthe plurality of SRSes is not greater than a certain threshold in thissituation described above.

When the transmission power of an SRS on a CC is too small, thetransmission signal cannot be correctly expressed with the resolution ofthe digital/analog (D/A) converter of the terminal (transmission side).However, the introduction of a threshold and dropping an SRS havingtransmission power not greater than the threshold make it possible toavoid unnecessary transmission processing (i.e., complex designing ofD/A taking into account (covering) low transmission power values)(consuming unnecessary transmission power can be avoided).

Power Scaling Method 9-A

In power scaling method 9-A, power scaling controlling section 109selects an SRS on a CC to be dropped (e.g., power allocation priority islowered, transmission power is reduced, transmission is stopped, ortransmission power is set equal to zero), in accordance with the lengthof the transmission cycle of a periodic SRS. Specifically, power scalingcontrolling section 109 selects a periodic SRS of a long transmissioncycle as the SRS on a CC to be preferentially dropped or a periodic SRSof a short transmission cycle as the SRS on a CC to be preferentiallydropped.

When an SRS of a long transmission cycle is selected as the SRS on a CCto be preferentially dropped, it is possible to obtain the same effectsas those obtained with power scaling method 3-A and also topreferentially follow short-term channel variation and achieves adaptivemodulation and channel coding (AMC) in accordance with short-term fadingvariation and also to control time-frequency domain scheduling with highaccuracy. Thus, UE-specific throughput and system throughput bymulti-user diversity can be improved.

When an SRS of a short transmission cycle is selected as the SRS on a CCto be preferentially dropped, it is possible to obtain the same effectsas those obtained with power scaling method 3-A and also to improve thelong-term channel measurement accuracy. Thus, cross-carrier schedulingcontrol, which adaptively selects a CC used for transmitting data andcontrol information, can be performed with high accuracy.

Power Scaling Method 10-A

In power scaling method 10-A, power scaling controlling section 109selects an SRS on a CC to be dropped (e.g., power allocation priority islowered, transmission power is reduced, transmission is stopped, ortransmission power is set equal to zero), in accordance with thebandwidth of each SRS. Specifically, an SRS having a wide bandwidth ispreferentially dropped over an SRS having a narrow bandwidth, or an SRShaving a narrow bandwidth is preferentially dropped over an SRS having awide bandwidth.

When an SRS having a wide bandwidth is preferentially dropped over anSRS having a narrow bandwidth, the following effects can be obtained.The transmission power of a UL channel (such as PUSCH and SRS) of LTE-A(LTE) is determined based on the transmission bandwidth and powerspectrum density (PSD). Thus, reducing the transmission power allocationpriority of an SRS having a wide bandwidth that has a large influence onthe size of the total transmission power makes it possible to minimizethe number of SRSes to be dropped. For example, provided that the totalbandwidth of SRSes on a plurality of CCs is defined as B, comparing thecase where the bandwidth of the SRS on one CC is B with the case wherethe bandwidth of each of the SRSes on two CCs is B/2, the number of CCsto be dropped can be smaller when the SRS on one CC is preferentiallydropped. Such a decrease in the number of CCs to be dropped is veryadvantageous when sounding on as many CCs as possible using SRSes isperformed to select a CC for transmitting data, control informationand/or the like. In addition, since a wider bandwidth involves largerintermodulation distortion, reducing the power allocation priority foran SRS having a wide bandwidth can reduce the influence of out-of-bandleakage (intermodulation distortion) over a wide range on a differentCC.

It is also possible to introduce a threshold into the bandwidthdetermination and to preferentially drop a corresponding SRS when abandwidth between SRSes or a difference between bandwidths of SRSesexceeds the threshold.

In addition, the larger the ratio of an SRS bandwidth to a CC bandwidth(e.g., SRS bandwidth/CC bandwidth) is, the more the power allocationpriority for the corresponding SRS on the CC may be lowered.

Meanwhile, when an SRS having a narrow bandwidth is preferentiallydropped over an SRS having a wide bandwidth, the following effects canbe obtained. When a high quality frequency resource is assigned bymeasuring a propagation channel over a wide bandwidth of only one CC, awide range frequency band can be measured at once.

It is also possible to introduce a threshold into the bandwidthdetermination and to drop a corresponding SRS when a bandwidth betweenSRSes or a difference between the bandwidths of the SRSes exceeds thethreshold.

In addition, the smaller the ratio of an SRS bandwidth to a CC bandwidth(e.g., SRS bandwidth/CC bandwidth) is, the more the power allocationpriority for the corresponding SRS on the CC may be lowered.

Power Scaling Method 11-A

In power scaling method 11-A, when a plurality of SRSes of Scells ispresent, power scaling controlling section 109 raises the powerallocation priority for the SRS on a CC on which UCI (such as CQI orPMI) reporting is triggered (to be triggered) by control informationincluded in a physical layer control channel PDCCH (UL or DL grant) orcontrol information reported (to be reported) via higher layersignaling, of the plurality of SRSes of the Scells. For example, powerscaling controlling section 109 raises the power allocation priority forthe SRS on the CC on which UCI reporting such as aperiodic CSI istriggered. Furthermore, on the basis of the priority for an Scell usedfor reporting periodic CQI (PMI) indicated via higher layer signalingsuch as radio resource control (RRC) from the eNB, power scalingcontrolling section 109 raises the power allocation priority for the SRSon the CC configured as an Scell with higher priority, for example.

Specifically, power scaling controlling section 109 raises the powerallocation priority for the SRS on the CC configured as an Scell withhigher priority indicated by the eNB among a Cell (CC) indicated by theeNB to transmit UCI with a PUSCH (to multiplex UCI on PUSCH) and a Cell(CC) on which UCI is transmitted with a PUSCH (UCI is multiplexed onPUSCH).

On the other hand, when a plurality of SRSes of Scells is present, powerscaling controlling section 109 lowers (preferentially drops, reducesthe transmission power, stops transmission, or sets the transmissionpower to be equal to zero) power allocation priority for the SRS on a CCon which no UCI (such as CQI or PMI) is triggered (has been triggered)by control information included in a physical layer control channel PDCC(UL or DL grant) or control information reported (to be reported) viahigher layer signaling, of the plurality of SRSes. For example, powerscaling controlling section 109 lowers the power allocation priority forthe SRS on a CC on which UCI reporting such as aperiodic CSI is nottriggered (has not been triggered) by any UL grant. Furthermore, on thebasis of the priority for an Scell used for reporting periodic CQI (PMI)indicated via higher layer signaling such as radio resource control(RRC) from the eNB, power scaling controlling section 109 lowers thepower allocation priority for the SRS on the CC configured as an Scellwith lower priority, for example.

Specifically, power scaling controlling section 109 lowers the powerallocation priority for the SRS of a Cell (CC) with lower priority amonga Cell (CC) indicated by the eNB not to transmit UCI with a PUSCH (tomultiplex UCI on PUSCH) and a Cell (CC) on which UCI is transmitted witha PUSCH (UCI is multiplexed on PUSCH).

The operation described above is used because an (e.g., aperiodic) SRSis likely to be transmitted on a CC which has been indicated by higherlayer signaling such as RRC from the eNB and which has higher priorityas an Scell used in reporting periodic CQI (PMI). This is becausequality measurement of such a Cell (CC) needs to be accurately performedbefore UCI transmission. In addition, if the power allocation priorityfor the (aperiodic) SRS to be transmitted on the CC is lowered (ordropped), MCS selection or transmission power control for UCI to betransmitted on a subsequent subframe is not correctly performed.

FIG. 14 illustrates an overview of power scaling method 11-A. As in thecases described above, the SRSes are simultaneously transmitted on thetwo CCs (CC#0 and CC#2) in FIG. 14. According to the control signalreported from the base station (via higher layer signaling), CC#0, CC#1,and CC#2 are configured as an Scell, Pcell, and Scell, respectively.When there is a plurality of transmission power values of SRS channelstransmitted on a plurality of CCs (when simultaneous transmission of aplurality of SRS channels occurs) in this situation, the powerallocation priority for the SRS on a CC on which UCI such as aperiodicCSI is triggered (to be triggered) by a UL grant is raised, of the twoSRSes of the two Scells. FIG. 14 illustrates a situation where UCI hasbeen triggered on the Scell of CC#2 in a previous subframe while no UCIhas been triggered on CC#0.

Accordingly, the same effects as those obtained with power scalingmethod 1-A can be obtained among a plurality of Scells (SCCs).

The priority for the Scell on which UCI has been triggered may be keptfor a certain period. Moreover, the priority for the Scell may be keptuntil UCI is triggered on a different CC. In addition, when there is aplurality of Scells on which UCI has been triggered, SRS power scalingmay be performed according to the latest trigger information. When thereis a plurality of Scells on which UCI has been triggered and also theUCI has been triggered at the same time, power scaling priority may bedetermined in accordance with UL CC ID numbers (in ascending ordescending order).

The priority order information for a CC on which UCI is transmitted andwhich is reported (indicated) by higher layer signaling among theplurality of Scells may be kept for a certain period (power scaling maybe performed in accordance with the information for a certainpredetermined period). Moreover, the priority order may be kept until anew priority order is reported (indicated) from the eNB via higher layersignaling. When the new priority order is reported (indicated), powerscaling may be performed according to the new priority order.

In addition, as described above, the power allocation priority for SRSeson CCs may be set based on the priority order of Scells which areindicated by higher layer signaling such as radio resource control (RRC)from the eNB and which are used for reporting periodic CQI (PMI). Forexample, the power allocation priority for the SRS is raised on a Cellhaving higher priority and indicated by the eNB among a Cell (CC)indicated by the eNB to transmit UCI with a PUSCH among a plurality ofScells and a Cell (CC) on which UCI is transmitted with a PUSCH among aplurality of Scells. On the other hand, the power allocation priorityfor the SRS is lowered on a Cell (CC) having lower priority andindicated by the eNB among a Cell (CC) indicated by the eNB not totransmit UCI with a PUSCH among a plurality of Scells and a Cell (CC) onwhich UCI is transmitted with a PUSCH among a plurality of Scells.

Accordingly, the same effects as those described above can be obtainedwith this configuration.

Moreover, it is also possible to keep (not to change) the transmissionpower (PSD) of an SRS of the Scell having the top priority based on thepriority order of Scells indicated by higher layer signaling such as RRCfrom the eNB and used for reporting periodic CQI (PMI).

Accordingly, it is possible to increase the accuracy in the qualitymeasurement of the Scell on which UCI is likely to be transmitted, whileobtaining the same effects as those described above. The eNB can reportappropriate transmission power (MCS) used in transmission of UCI to theterminal.

Moreover, it is also possible to select an Scell with lower priority asthe SRS to be dropped, based on the priority order of Scells indicatedby higher layer signaling such as RRC from the eNB and used forreporting periodic CQI (PMI). For example, it is possible to keep (notto change) the transmission power (PSD) of the SRS of the Scell with thetop priority and to drop (to set the transmission power to be equal tozero, set the PSD to be equal to zero, or reduce the transmission power)all the transmission power of SRSes of the other Scells.

Accordingly, the same effects as those obtained by power scaling method3-A can be obtained among a plurality of Scells. More specifically, whena plurality of SRSes is all simultaneously transmitted using a Pcell anda plurality of Scells, the same effects as those described above can beobtained. It is also possible to drop (to set the transmission power tobe equal to zero, stop the transmission or set the PSD to be equal tozero) the SRSes of Scells in ascending order of priority of Scells(CCs). Accordingly, the same effects as those described above can beobtained with this configuration.

In the abovementioned method, the eNB (not illustrated) determines thepriority order for each terminal for an Scell used in reporting periodicCQI (PMI) or the like among a plurality of Scells or selects a Cell (CC)for each terminal for transmitting UCI with a PUSCH (UCI is multiplexedon PUSCH) among a plurality of Scells, using Scell or Pcell informationset for each terminal and/or an uplink interfered state for each CC(Cell), for example. The determined or selected information such aspriority order is reported to the terminal using higher layer signaling(RCC). The terminal that has received the information uses theinformation for power scaling when simultaneous transmission on aplurality of UL channels occurs.

Power Scaling Method 12-A

In power scaling method 12-A, power scaling controlling section 109preferentially drops an SRS having a low PSD over an SRS having a highPSD (lowers the power allocation priority, reduces the transmissionpower, stops the transmission, or sets the transmission power to beequal to zero).

When a difference in PSD of SRS between CCs is large, theintermodulation distortion of the SRS on the CC having a higher PSD maybecome larger than a PSD of an SRS on a different CC. Thisintermodulation distortion cannot be removed by a transmission filter.Specifically, when the SRS is transmitted without removal of theintermodulation distortion, the eNB measures the communication qualityof the CC by the SRS affected by the intermodulation distortion. As aresult, correct scheduling or transmission power control cannot beperformed. With respect to this problem, transmission of only an SRShaving a high PSD, which is unlikely to be affected by theintermodulation distortion, allows an eNB to perform measurement on theCC with high accuracy.

FIG. 15 illustrates an overview of power scaling method 12-A. In FIG.15, as in the cases described above, the SRSes are simultaneouslytransmitted on the two CCs (CC#0 and CC#1) in FIG. 15. According to thecontrol signal reported from the base station (via higher layersignaling), CC#0 and CC#1 are each configured as an Scell. In FIG. 15,the dotted line indicates harmonic distortion (intermodulationdistortion). Under this condition, an SRS having a low PSD that islikely to be affected by intermodulation distortion is dropped.

It should be noted that, a transmission power control parameter (PUSCHor SRS) related to calculating a PSD value may be used to determine theSRS to be dropped. Examples of the parameter includes a TPC commandaccumulation value, transport block size, offset parameter related to anMCS level (TF), SRS offset value with respect to PUSCH transmissionpower, and the number of bits per RE (TB size/the number of allocatedREs). When these values are high, the corresponding SRS has a higherPSD. Thus, the SRS to be dropped may be determined based on thesevalues. In addition, when the number of allocated resource elements(REs) or the number of allocated subcarriers is small, the correspondingSRS has a higher PSD. Thus, the SRS to be dropped may be determinedbased on these values.

In addition, it is also possible to introduce a threshold for PSDs orthe abovementioned parameters and to preferentially drop thecorresponding SRS when these values exceed the threshold.

As described above, according to Embodiment 2, when a plurality of SRSesis simultaneously transmitted using a Pcell and Scell, transmissionpower is preferentially allocated with respect to the SRS of a Pcellover the SRS of an Scell. Thus, it is possible to reduce the probabilityof a CC that transmits an SRS with low power allocation priority beingidentical to a CC on which UCI is multiplexed. Accordingly, thepropagation channel quality information on a Pcell on which UCI islikely to be multiplexed can be estimated with high accuracy using anSRS with high power allocation priority, which in turn allows the eNB toindicate appropriate transmission power for a subsequent UL channel onwhich UCI is to be transmitted.

It should be noted that, although the description has been givenregarding the situation between CCs, the methods described above may beapplied to a plurality of SRSes on a CC.

In addition, the power scaling methods described above may be used incombination.

Moreover, the methods that have been described with an assumption thatthey are applied to a plurality of SRSes on a plurality of Scells may beapplied in the same manner when a plurality of SRSes on a Pcell or aplurality of SRSes on a plurality of Pcells is present.

Furthermore, as a method of reducing the transmission power of an SRSwith low power allocation priority described above, an SRS scalingweight reported from an eNB to a terminal (via higher layer signaling)may be used to reduce the transmission power. When w_Pcell_SRS andw_Scell_SRS are defined as the scaling weights applied to SRSes of aPcell and Scell, respectively, the scaling weights may be set (defined)to satisfy w_Pcell_SRS>w_Scell_SRS. Alternatively, the scaling weightsmay be defined to satisfy w_Pcell_SRS=1, and w_Scell_SRS<1. For dropping(stopping the transmission or setting the transmission power to be equalto zero), it is possible to set w_Scell_SRS=0.

In addition, the power scaling methods described above may be used incombination. Combining the power scaling methods according toEmbodiments 1 and 2 enables performing power scaling when the totalvalue of transmission power of a plurality of uplink channelstransmitted on a plurality of CCs (Cells) does not exceed theUE-specific maximum transmission power, and also when simultaneoustransmission of a plurality of uplink channels on a plurality of CCsoccurs. An exemplary combined method (power scaling method 16-A) inwhich power scaling methods 3(3-A) and 12(12-A) according to Embodiment1(2) are combined will be described hereinafter.

Power Scaling Method 16-A

In power scaling method 16-A, when a plurality of SRSes is present on aplurality of Scells, power scaling controlling section 109 determinespower allocation priority for an SRS based on a transport block (TB)size of a PUSCH included in a UL grant reported to a terminal from theeNB.

When the size of UCI is large (the number of bits is large), therearises a problem in that UCI of CQI or PMI cannot be multiplexed on aPUSCH with a small TB size. When CQI or PMI information on a pluralityof CCs is reported to the eNB using a PUSCH of a single Scell, thisproblem becomes more significant. The method of reporting theinformation through division of UCI into a plurality of PUSCHs is notfavorable in considering the influence on the PA as described above, forexample, since such division results in UL multi-carrier transmission.Accordingly, it is favorable to employ a method to multiplex UCI on aPUSCH having a larger TB size, when a plurality of PUSCHs is assigned toa plurality of Scells.

Accordingly, in power scaling method 16-A, the priority for thetransmission power of the SRS on a CC (Cell) transmitting a PUSCH towhich a large size TB is mapped is raised among a plurality of Scells,for example. Meanwhile, the priority for the transmission power of theSRS on a CC (Cell) transmitting a PUSCH on which a small size TB ismapped is lowered.

In the method described above, the priority for the transmission powerof the SRS on a CC (Cell) on which a PUSCH of a large size TB istransmitted may be raised, while the priority for the transmission powerof the SRSes of the other Scells (CCs) is lowered.

It is also possible to keep (not to change) the transmission power ofthe SRS on a CC (Cell) on which a PUSCH of a large size TB istransmitted, while reducing the transmission power of the SRSes of theother Scells (CCs).

It is also possible to keep (not to change) the transmission power ofthe SRS on a CC (Cell) on which a PUSCH of a large size TB istransmitted, while dropping (setting the transmission power to be equalto zero, stopping the transmission, or setting the PSD to be equal tozero) the SRSes of the other Scells (CCs).

It is also possible to drop (to set the transmission power to be equalto zero, stop the transmission, or set the PSD to be equal to zero) theSRSes in ascending order of the TB sizes of the PUSCHs respectivelytransmitted using the Scells (CCs).

Accordingly, the same effects as those obtained by the methods in theembodiments described above can be obtained.

The power allocation priority for the SRSes that is set according topower scaling method 16-A may be kept for a certain predeterminedperiod. In addition, the priority may be kept among a plurality ofScells until combinations of a plurality of TB sizes different among aplurality of Scells are transmitted again. Moreover, SRS power scalingmay be performed according to the latest priority with respect to thepower allocation priority for the SRSes that is set according to powerscaling method 16-A.

The above-noted embodiments have been described by examples of hardwareimplementations, but the present invention can be also implemented bysoftware in conjunction with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor, whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

Each of the embodiments has been described with antennas, but thepresent invention can be applied to antenna ports in the same manner.

The term “antenna port” refers to a logical antenna including one ormore physical antennas. In other words, the term “antenna port” does notnecessarily refer to a single physical antenna, and may sometimes referto an antenna array formed of a plurality of antennas, and/or the like.

For example, 3GPP LTE does not specify the number of physical antennasforming an antenna port, but specifies an antenna port as a minimum unitallowing each base station to transmit a different reference signal.

In addition, an antenna port may be specified as a minimum unit formultiplication of precoding vector weighting.

The disclosures of the specifications, the drawings, and the abstractsof Japanese Patent Application No. 2010-249005, filed on Nov. 5, 2010,and Japanese Patent Application No. 2010-258360, filed on Nov. 18, 2010,are incorporated herein by reference in their entirety.

INDUSTRIAL APPLICABILITY

The radio communication apparatus and power allocation method accordingto the present invention can be applied to mobile communication systemssuch as LTE-A.

REFERENCE SIGNS LIST

-   -   101 Antenna    -   102 Radio reception processing section    -   103 OFDM demodulating section    -   104 Demodulating section    -   105 Channel decoding section    -   106 Control information extracting section    -   107 Transmission power calculating section    -   108 Power scaling detecting section    -   109 Power scaling controlling section    -   110-1 to 110-N Coding and modulation section    -   111-1 to 111-N Multiplexing section    -   112-1 to 112-N Transmission power setting section    -   113-1 to 113-N SC-FDMA modulation section    -   114 Combining section    -   115 Radio transmission processing section

1. A radio communication terminal apparatus comprising: transmissionpower calculating circuitry which, in operation, calculates transmissionpower of a plurality of uplink channels on a plurality of componentcarriers of carrier aggregation; power scaling detecting circuitrywhich, in operation, detects, using the calculated transmission power,whether or not a total value of the transmission power of the uplinkchannels transmitted on the plurality of component carriers exceedsmaximum transmission power specific to the terminal apparatus andwhether or not power scaling occurs as a result; and power scalingcontrolling circuitry which, in operation, preferentially allocates,when the power scaling detecting circuitry detects that power scalingoccurs and when a plurality of reference signals is transmitted using aprimary cell and a secondary cell, transmission power with respect to areference signal of the primary cell over a reference signal of thesecondary cell.
 2. The radio communication terminal apparatus accordingto claim 1, wherein the power scaling controlling circuitry, inoperation, sets transmission power of the reference signal of theprimary cell to be not greater than component carrier specific maximumtransmission power, keeps the transmission power of the reference signalof the primary cell and reduces transmission power of the referencesignal of the secondary cell.
 3. The radio communication terminalapparatus according to claim 1, wherein the power scaling controllingcircuitry, in operation, keeps transmission power of the referencesignal of the primary cell, and stops transmission of the referencesignal of the secondary cell or sets transmission power of the referencesignal of the secondary cell to be equal to zero.
 4. The radiocommunication terminal apparatus according to claim 1, wherein, whenthere is a plurality of reference signals of the secondary cell, thepower scaling controlling circuitry reduces transmission power of thereference signals of the secondary cell, stops transmission thereof, orsets transmission power thereof to be equal to zero in ascending orderof the transmission power of the reference signals of the secondarycell.
 5. The radio communication terminal apparatus according to claim1, wherein, when there is a plurality of reference signals of thesecondary cell, the power scaling controlling circuitry uniformlyreduces transmission power of the plurality of reference signals of thesecondary cell.
 6. The radio communication terminal apparatus accordingto claim 1, wherein, when there is a plurality of reference signals ofthe secondary cell, the power scaling controlling circuitry stopstransmission of all of the plurality of reference signals of thesecondary cell or sets the transmission power thereof to be equal tozero.
 7. The radio communication terminal apparatus according to claim1, wherein, when transmission power of the reference signal of thesecondary cell is not greater than a threshold, the power scalingcontrolling circuitry reduces the transmission power of the referencesignal of the secondary cell, stops transmission of the reference signalof the secondary cell, or sets the transmission power of the referencesignal of the secondary cell to be equal to zero.
 8. The radiocommunication terminal apparatus according to claim 1, wherein, when thereference signal of the secondary cell has transmission power thatdiffers, by at least a predetermined value, from a largest transmissionpower among a plurality of reference signals, the power scalingcontrolling circuitry reduces transmission power of the reference signalof the secondary cell, stops transmission of the reference signal of thesecondary cell, or sets the transmission power of the reference signalof the secondary cell to be equal to zero.
 9. The radio communicationterminal apparatus according to claim 1, wherein the power scalingcontrolling circuitry, in operation, lowers power allocation priority,reduces transmission power, stops transmission, or sets the transmissionpower to be equal to zero for a reference signal having a low powerspectrum density rather than a reference signal having a high powerspectrum density.
 10. The radio communication terminal apparatusaccording to claim 1, wherein the power scaling controlling circuitry,in operation, selects a reference signal on a component carrier inaccordance with a bandwidth of the reference signal and lowers powerallocation priority for the selected reference signal, reducestransmission power of the selected reference signal, stops transmissionthereof, or sets the transmission power thereof to be equal to zero. 11.The radio communication terminal apparatus according to claim 10,wherein the power scaling controlling circuitry, in operation, selects areference signal having a wide bandwidth rather than a reference signalhaving a narrow bandwidth.
 12. The radio communication terminalapparatus according to claim 10, wherein the power scaling controllingcircuitry, in operation, selects a reference signal having a narrowbandwidth rather than a reference signal having a wide bandwidth. 13.The radio communication terminal apparatus according to claim 1, whereinthe power scaling controlling circuitry, in operation, raises powerallocation priority for a reference signal on a component carrier onwhich uplink control information is triggered and lowers powerallocation priority for a reference signal on a component carrier onwhich the uplink control information is not triggered among referencesignals of a plurality of secondary cells.
 14. A power allocation methodcomprising: calculating transmission power of a plurality of uplinkchannels on a plurality of component carriers of carrier aggregation;detecting, using the calculated transmission power, whether or not atotal value of the transmission power of the uplink channels transmittedon the plurality of component carriers exceeds maximum transmissionpower specific to a corresponding terminal apparatus and whether or notpower scaling occurs as a result; and preferentially allocating, whendetecting that power scaling occurs and when a plurality of referencesignals is transmitted using a primary cell and a secondary cell,transmission power with respect to a reference signal of the primarycell over a reference signal of the secondary cell.